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#1
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I have the home and student 2007 version. When graphing a scatter graph with
the Y axis having 10 to the negative power, excel doesn't show the values on the y axis. It only shows the 0 intercept value. I've tried editing the axis values but the number still doesn't display and excel automatically puts the number to at least 10 decimal places, ie 5.000000000000001E-19. When I just click automatic, the right values appear in the edit menu but the y values still won't show on the actual graph. So when doing a trendline the equation doesn't show an m slope value, ie y=5E-19. A friend graphed my data on an older version excel and it graphed it properly with the proper y values displaying, and linear trendline equation was in right format of y = mx + b, ie y= -2E-18x + 5E-19 Could my software be defective? Or are some features disabled? |
#2
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It would be helpful to see at least 5 data points (both the x and the y
values): could you list them for us? Are you sure you have made an XY chart and not a Line chart? If you wish you may send me a file with the data best wishes -- Bernard V Liengme www.stfx.ca/people/bliengme remove caps from email "Lala" wrote in message ... I have the home and student 2007 version. When graphing a scatter graph with the Y axis having 10 to the negative power, excel doesn't show the values on the y axis. It only shows the 0 intercept value. I've tried editing the axis values but the number still doesn't display and excel automatically puts the number to at least 10 decimal places, ie 5.000000000000001E-19. When I just click automatic, the right values appear in the edit menu but the y values still won't show on the actual graph. So when doing a trendline the equation doesn't show an m slope value, ie y=5E-19. A friend graphed my data on an older version excel and it graphed it properly with the proper y values displaying, and linear trendline equation was in right format of y = mx + b, ie y= -2E-18x + 5E-19 Could my software be defective? Or are some features disabled? |
#3
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Yes the graph choosen is the xy scatter graph. The values I'm trying to graph
are : x = 0.1111 y= 2.872*10^-19 ; (2.872E-19 when actually posting in the cell) x = 0.0625 y= 4.043*10^-19 ; (4.043E-19) x = 0.0400 y= 4.576*10^-19 ; (4.576E-19) x = 0.0277 y= 4.814*10^-19 ; (4.814E-19) Again the Y values of (1E-19 to 6E-19) are not posting, only 0 value is posting. When editing the y axis the minimum value on automatic is 0 and the maximum does say 6.0E-19. But on the actual agraph I don't see these values. So when doing a line graph I only get a linear equation of y=5E-19 instead of y=mx+b. Excel does graph the data points and when adding data labels, the values appear. It's just the division values (1.00E-19 to 6.00E-19) on the y axis that doesn't appear. I've also tried setting the cells to scientific numbers, general and numbers but that didn't help. It has to be the program because I've had 2 people graph my data and it worked on their software. "Bernard Liengme" wrote: It would be helpful to see at least 5 data points (both the x and the y values): could you list them for us? Are you sure you have made an XY chart and not a Line chart? If you wish you may send me a file with the data best wishes -- Bernard V Liengme www.stfx.ca/people/bliengme remove caps from email "Lala" wrote in message ... I have the home and student 2007 version. When graphing a scatter graph with the Y axis having 10 to the negative power, excel doesn't show the values on the y axis. It only shows the 0 intercept value. I've tried editing the axis values but the number still doesn't display and excel automatically puts the number to at least 10 decimal places, ie 5.000000000000001E-19. When I just click automatic, the right values appear in the edit menu but the y values still won't show on the actual graph. So when doing a trendline the equation doesn't show an m slope value, ie y=5E-19. A friend graphed my data on an older version excel and it graphed it properly with the proper y values displaying, and linear trendline equation was in right format of y = mx + b, ie y= -2E-18x + 5E-19 Could my software be defective? Or are some features disabled? |
#4
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I had no trouble getting a chart with your data. The slope is -2.35E-18 and
intercept 5.49E-19 Since your cells have entries such as =2.872*10^-19 which display as 2.872E-19, it would appear you have real numbers and not text. A bit of a mystery! You have not set the y scale min & max to anything other than 'automatic' have you? What do you get with =SLOPE(B2:B5, A2:A5) - the B range holds the y-values, A range the x-values. ? Have you tried a new workbook entering values like this x y 1 1E-10 2 2E-10 3 3E-10 4 4E-10 can you get a chart with these values? By the way: if I was working with numbers like yours (but as a scientist I cannot think of anything that small that I could measure!) I would use x = 0.1111 y= 2.872 x = 0.0625 y= 4.043 x = 0.0400 y= 4.576 x = 0.0277 y= 4.814 Then I would scale the resulting slope and intercept by a factor of 10^-19 Happy to look at a file if you send me one to my private email (not newsgroup) Bernard V Liengme www.stfx.ca/people/bliengme remove caps from email "Lala" wrote in message ... Yes the graph choosen is the xy scatter graph. The values I'm trying to graph are : x = 0.1111 y= 2.872*10^-19 ; (2.872E-19 when actually posting in the cell) x = 0.0625 y= 4.043*10^-19 ; (4.043E-19) x = 0.0400 y= 4.576*10^-19 ; (4.576E-19) x = 0.0277 y= 4.814*10^-19 ; (4.814E-19) Again the Y values of (1E-19 to 6E-19) are not posting, only 0 value is posting. When editing the y axis the minimum value on automatic is 0 and the maximum does say 6.0E-19. But on the actual agraph I don't see these values. So when doing a line graph I only get a linear equation of y=5E-19 instead of y=mx+b. Excel does graph the data points and when adding data labels, the values appear. It's just the division values (1.00E-19 to 6.00E-19) on the y axis that doesn't appear. I've also tried setting the cells to scientific numbers, general and numbers but that didn't help. It has to be the program because I've had 2 people graph my data and it worked on their software. "Bernard Liengme" wrote: It would be helpful to see at least 5 data points (both the x and the y values): could you list them for us? Are you sure you have made an XY chart and not a Line chart? If you wish you may send me a file with the data best wishes -- Bernard V Liengme www.stfx.ca/people/bliengme remove caps from email "Lala" wrote in message ... I have the home and student 2007 version. When graphing a scatter graph with the Y axis having 10 to the negative power, excel doesn't show the values on the y axis. It only shows the 0 intercept value. I've tried editing the axis values but the number still doesn't display and excel automatically puts the number to at least 10 decimal places, ie 5.000000000000001E-19. When I just click automatic, the right values appear in the edit menu but the y values still won't show on the actual graph. So when doing a trendline the equation doesn't show an m slope value, ie y=5E-19. A friend graphed my data on an older version excel and it graphed it properly with the proper y values displaying, and linear trendline equation was in right format of y = mx + b, ie y= -2E-18x + 5E-19 Could my software be defective? Or are some features disabled? |
#5
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Without doing anything special, I created a chart and added a trendline. It
worked as expected, and I got this formula: y = -2.3507E-18x + 5.4943E-19 R2 = 9.9921E-01 This worked the same in Excel 2000 and in 2003. Then I tried it in Excel 2007 and it failed in the same manner that you described. The Y axis only showed 0.0000E00 at the bottom, and no more values, and the formula showed Y = 5.4943E-19, omitting the constant. Excel apparently thought this was a rounding error and coerced it to zero. I ran a set of trials where I multiplied the Y values of each trial by ten to get the Y values for the next. My regression formulas looked like: y = 5.49429E-19 [R² = 9.99213E-01] y = 5.49429E-18 [R² = 9.99213E-01] y = 5.49429E-17 [R² = 9.99213E-01] y = 5.49429E-16 [R² = 9.99213E-01] y = -2.35066E-14x [R² = 9.99213E-01] y = -2.35066E-13x + 5.49429E-14 [R² = 9.99213E-01] y = -2.35066E-12x + 5.49429E-13 [R² = 9.99213E-01] y = -2.35066E-11x + 5.49429E-12 [R² = 9.99213E-01] The first formula came from your example. Note that the constant has the same pre-exponential factor for all of the formulas (5.49429) except for the case when it would be 5.49429E-15, which sounds like a threshold for being considered a rounding error. In all cases where the coefficient of X wasn't ignored, the coefficient's pre-exponential factor was the same (-2.35066), and in all cases, R² was the same (0.999213). I repeated this in Excel 2003, and the formulas were identical except for the exponents of the fitting constants. I'd classify this one more as a bug than as a feature. - Jon ------- Jon Peltier, Microsoft Excel MVP Tutorials and Custom Solutions http://PeltierTech.com _______ "Lala" wrote in message ... Yes the graph choosen is the xy scatter graph. The values I'm trying to graph are : x = 0.1111 y= 2.872*10^-19 ; (2.872E-19 when actually posting in the cell) x = 0.0625 y= 4.043*10^-19 ; (4.043E-19) x = 0.0400 y= 4.576*10^-19 ; (4.576E-19) x = 0.0277 y= 4.814*10^-19 ; (4.814E-19) Again the Y values of (1E-19 to 6E-19) are not posting, only 0 value is posting. When editing the y axis the minimum value on automatic is 0 and the maximum does say 6.0E-19. But on the actual agraph I don't see these values. So when doing a line graph I only get a linear equation of y=5E-19 instead of y=mx+b. Excel does graph the data points and when adding data labels, the values appear. It's just the division values (1.00E-19 to 6.00E-19) on the y axis that doesn't appear. I've also tried setting the cells to scientific numbers, general and numbers but that didn't help. It has to be the program because I've had 2 people graph my data and it worked on their software. "Bernard Liengme" wrote: It would be helpful to see at least 5 data points (both the x and the y values): could you list them for us? Are you sure you have made an XY chart and not a Line chart? If you wish you may send me a file with the data best wishes -- Bernard V Liengme www.stfx.ca/people/bliengme remove caps from email "Lala" wrote in message ... I have the home and student 2007 version. When graphing a scatter graph with the Y axis having 10 to the negative power, excel doesn't show the values on the y axis. It only shows the 0 intercept value. I've tried editing the axis values but the number still doesn't display and excel automatically puts the number to at least 10 decimal places, ie 5.000000000000001E-19. When I just click automatic, the right values appear in the edit menu but the y values still won't show on the actual graph. So when doing a trendline the equation doesn't show an m slope value, ie y=5E-19. A friend graphed my data on an older version excel and it graphed it properly with the proper y values displaying, and linear trendline equation was in right format of y = mx + b, ie y= -2E-18x + 5E-19 Could my software be defective? Or are some features disabled? |
#6
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The secret was in the OP's first line:
I have the home and student 2007 version. Microsoft has "improved" their treatment of tiny rounding errors by arbitrarily assuming certain small values are really supposed to be zero. The ignored values are less then or around 1E-15, which corresponds to the missing values in my testing (see my other post). This has messed up the trendline regression formula, which used to be considered the best in the business. LINEST calculates the regression coefficients properly, at least in 2003 and 2007 (I didn't bother to test prior to this). - Jon ------- Jon Peltier, Microsoft Excel MVP Tutorials and Custom Solutions http://PeltierTech.com _______ "Bernard Liengme" wrote in message ... I had no trouble getting a chart with your data. The slope is -2.35E-18 and intercept 5.49E-19 Since your cells have entries such as =2.872*10^-19 which display as 2.872E-19, it would appear you have real numbers and not text. A bit of a mystery! You have not set the y scale min & max to anything other than 'automatic' have you? What do you get with =SLOPE(B2:B5, A2:A5) - the B range holds the y-values, A range the x-values. ? Have you tried a new workbook entering values like this x y 1 1E-10 2 2E-10 3 3E-10 4 4E-10 can you get a chart with these values? By the way: if I was working with numbers like yours (but as a scientist I cannot think of anything that small that I could measure!) I would use x = 0.1111 y= 2.872 x = 0.0625 y= 4.043 x = 0.0400 y= 4.576 x = 0.0277 y= 4.814 Then I would scale the resulting slope and intercept by a factor of 10^-19 Happy to look at a file if you send me one to my private email (not newsgroup) Bernard V Liengme www.stfx.ca/people/bliengme remove caps from email "Lala" wrote in message ... Yes the graph choosen is the xy scatter graph. The values I'm trying to graph are : x = 0.1111 y= 2.872*10^-19 ; (2.872E-19 when actually posting in the cell) x = 0.0625 y= 4.043*10^-19 ; (4.043E-19) x = 0.0400 y= 4.576*10^-19 ; (4.576E-19) x = 0.0277 y= 4.814*10^-19 ; (4.814E-19) Again the Y values of (1E-19 to 6E-19) are not posting, only 0 value is posting. When editing the y axis the minimum value on automatic is 0 and the maximum does say 6.0E-19. But on the actual agraph I don't see these values. So when doing a line graph I only get a linear equation of y=5E-19 instead of y=mx+b. Excel does graph the data points and when adding data labels, the values appear. It's just the division values (1.00E-19 to 6.00E-19) on the y axis that doesn't appear. I've also tried setting the cells to scientific numbers, general and numbers but that didn't help. It has to be the program because I've had 2 people graph my data and it worked on their software. "Bernard Liengme" wrote: It would be helpful to see at least 5 data points (both the x and the y values): could you list them for us? Are you sure you have made an XY chart and not a Line chart? If you wish you may send me a file with the data best wishes -- Bernard V Liengme www.stfx.ca/people/bliengme remove caps from email "Lala" wrote in message ... I have the home and student 2007 version. When graphing a scatter graph with the Y axis having 10 to the negative power, excel doesn't show the values on the y axis. It only shows the 0 intercept value. I've tried editing the axis values but the number still doesn't display and excel automatically puts the number to at least 10 decimal places, ie 5.000000000000001E-19. When I just click automatic, the right values appear in the edit menu but the y values still won't show on the actual graph. So when doing a trendline the equation doesn't show an m slope value, ie y=5E-19. A friend graphed my data on an older version excel and it graphed it properly with the proper y values displaying, and linear trendline equation was in right format of y = mx + b, ie y= -2E-18x + 5E-19 Could my software be defective? Or are some features disabled? |
#7
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Hi Jon,
Yes, I overlooked the mention of 2007! But as I said to OP, if is hard to imagine a use of such small numbers and a y-axis transformation will work even in XL2007. As you know better than I, MS have been trying hard to avoid the 'nasty' tiny numbers that should be zero but are not because of 'binary round off errors'. We getting fewer questions about that topic with XL2003 becoming more popular. So I cannot fault MS too much on this score! Cheers -- Bernard V Liengme www.stfx.ca/people/bliengme remove caps from email "Jon Peltier" wrote in message ... The secret was in the OP's first line: I have the home and student 2007 version. Microsoft has "improved" their treatment of tiny rounding errors by arbitrarily assuming certain small values are really supposed to be zero. The ignored values are less then or around 1E-15, which corresponds to the missing values in my testing (see my other post). This has messed up the trendline regression formula, which used to be considered the best in the business. LINEST calculates the regression coefficients properly, at least in 2003 and 2007 (I didn't bother to test prior to this). - Jon ------- Jon Peltier, Microsoft Excel MVP Tutorials and Custom Solutions http://PeltierTech.com _______ "Bernard Liengme" wrote in message ... I had no trouble getting a chart with your data. The slope is -2.35E-18 and intercept 5.49E-19 Since your cells have entries such as =2.872*10^-19 which display as 2.872E-19, it would appear you have real numbers and not text. A bit of a mystery! You have not set the y scale min & max to anything other than 'automatic' have you? What do you get with =SLOPE(B2:B5, A2:A5) - the B range holds the y-values, A range the x-values. ? Have you tried a new workbook entering values like this x y 1 1E-10 2 2E-10 3 3E-10 4 4E-10 can you get a chart with these values? By the way: if I was working with numbers like yours (but as a scientist I cannot think of anything that small that I could measure!) I would use x = 0.1111 y= 2.872 x = 0.0625 y= 4.043 x = 0.0400 y= 4.576 x = 0.0277 y= 4.814 Then I would scale the resulting slope and intercept by a factor of 10^-19 Happy to look at a file if you send me one to my private email (not newsgroup) Bernard V Liengme www.stfx.ca/people/bliengme remove caps from email "Lala" wrote in message ... Yes the graph choosen is the xy scatter graph. The values I'm trying to graph are : x = 0.1111 y= 2.872*10^-19 ; (2.872E-19 when actually posting in the cell) x = 0.0625 y= 4.043*10^-19 ; (4.043E-19) x = 0.0400 y= 4.576*10^-19 ; (4.576E-19) x = 0.0277 y= 4.814*10^-19 ; (4.814E-19) Again the Y values of (1E-19 to 6E-19) are not posting, only 0 value is posting. When editing the y axis the minimum value on automatic is 0 and the maximum does say 6.0E-19. But on the actual agraph I don't see these values. So when doing a line graph I only get a linear equation of y=5E-19 instead of y=mx+b. Excel does graph the data points and when adding data labels, the values appear. It's just the division values (1.00E-19 to 6.00E-19) on the y axis that doesn't appear. I've also tried setting the cells to scientific numbers, general and numbers but that didn't help. It has to be the program because I've had 2 people graph my data and it worked on their software. "Bernard Liengme" wrote: It would be helpful to see at least 5 data points (both the x and the y values): could you list them for us? Are you sure you have made an XY chart and not a Line chart? If you wish you may send me a file with the data best wishes -- Bernard V Liengme www.stfx.ca/people/bliengme remove caps from email "Lala" wrote in message ... I have the home and student 2007 version. When graphing a scatter graph with the Y axis having 10 to the negative power, excel doesn't show the values on the y axis. It only shows the 0 intercept value. I've tried editing the axis values but the number still doesn't display and excel automatically puts the number to at least 10 decimal places, ie 5.000000000000001E-19. When I just click automatic, the right values appear in the edit menu but the y values still won't show on the actual graph. So when doing a trendline the equation doesn't show an m slope value, ie y=5E-19. A friend graphed my data on an older version excel and it graphed it properly with the proper y values displaying, and linear trendline equation was in right format of y = mx + b, ie y= -2E-18x + 5E-19 Could my software be defective? Or are some features disabled? |
#8
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Pardon my ignorance, but what changed in this regard with Excel 2003? I am
only aware of the unfortunate (IMHO) fuzz factor introduced in Excel 97 (MS calls it an "optimization") http://support.microsoft.com/kb/78113 with the result that =a-b and =(a-b) are no longer guaranteed to give the same result. It probably did avoid a few easy questions about "why isn't my result zero", but created a whole new genre of harder questions dealing with the fundamental (in)consistency of Excel's arithmetic. Jerry "Bernard Liengme" wrote: Hi Jon, Yes, I overlooked the mention of 2007! But as I said to OP, if is hard to imagine a use of such small numbers and a y-axis transformation will work even in XL2007. As you know better than I, MS have been trying hard to avoid the 'nasty' tiny numbers that should be zero but are not because of 'binary round off errors'. We getting fewer questions about that topic with XL2003 becoming more popular. So I cannot fault MS too much on this score! Cheers -- Bernard V Liengme www.stfx.ca/people/bliengme remove caps from email |
#9
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This is not a numerically challenging calculation, so LINEST in Excel 2000
agrees with the chart trendline to 15 figures. I do wish that MS would stop digging this hole deeper. Jerry "Jon Peltier" wrote: The secret was in the OP's first line: I have the home and student 2007 version. Microsoft has "improved" their treatment of tiny rounding errors by arbitrarily assuming certain small values are really supposed to be zero. The ignored values are less then or around 1E-15, which corresponds to the missing values in my testing (see my other post). This has messed up the trendline regression formula, which used to be considered the best in the business. LINEST calculates the regression coefficients properly, at least in 2003 and 2007 (I didn't bother to test prior to this). - Jon ------- Jon Peltier, Microsoft Excel MVP Tutorials and Custom Solutions http://PeltierTech.com |
#10
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Amazing, isn't it? I reported it, but I doubt I'm the first.
- Jon ------- Jon Peltier, Microsoft Excel MVP Tutorials and Custom Solutions http://PeltierTech.com _______ "Jerry W. Lewis" wrote in message ... This is not a numerically challenging calculation, so LINEST in Excel 2000 agrees with the chart trendline to 15 figures. I do wish that MS would stop digging this hole deeper. Jerry "Jon Peltier" wrote: The secret was in the OP's first line: I have the home and student 2007 version. Microsoft has "improved" their treatment of tiny rounding errors by arbitrarily assuming certain small values are really supposed to be zero. The ignored values are less then or around 1E-15, which corresponds to the missing values in my testing (see my other post). This has messed up the trendline regression formula, which used to be considered the best in the business. LINEST calculates the regression coefficients properly, at least in 2003 and 2007 (I didn't bother to test prior to this). - Jon ------- Jon Peltier, Microsoft Excel MVP Tutorials and Custom Solutions http://PeltierTech.com |
#11
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Maybe I misspoke but it seems the newsgroup gets fewer question on this
topic now. I had thought XL2003 had improved the "optimization" Was is really as long ago as XL97! Sorry for the confusion. best wishes -- Bernard V Liengme www.stfx.ca/people/bliengme remove caps from email "Jerry W. Lewis" wrote in message ... Pardon my ignorance, but what changed in this regard with Excel 2003? I am only aware of the unfortunate (IMHO) fuzz factor introduced in Excel 97 (MS calls it an "optimization") http://support.microsoft.com/kb/78113 with the result that =a-b and =(a-b) are no longer guaranteed to give the same result. It probably did avoid a few easy questions about "why isn't my result zero", but created a whole new genre of harder questions dealing with the fundamental (in)consistency of Excel's arithmetic. Jerry "Bernard Liengme" wrote: Hi Jon, Yes, I overlooked the mention of 2007! But as I said to OP, if is hard to imagine a use of such small numbers and a y-axis transformation will work even in XL2007. As you know better than I, MS have been trying hard to avoid the 'nasty' tiny numbers that should be zero but are not because of 'binary round off errors'. We getting fewer questions about that topic with XL2003 becoming more popular. So I cannot fault MS too much on this score! Cheers -- Bernard V Liengme www.stfx.ca/people/bliengme remove caps from email |
#12
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Changed y scale min and maxt to fixed, thinking that might help, when nothing
happened changed it back to automatic. As for the numbers being small. The graph was supppose to give me the Rydberg constant (from the slope) based on a spectroscopy reading of a hydrogen light. Thanks for all the help and giving me the full y formula values. The other post about excel just assuming that any number smaller than 10^-10 is 0 answered my main question about the disappearing y values. "Bernard Liengme" wrote: I had no trouble getting a chart with your data. The slope is -2.35E-18 and intercept 5.49E-19 Since your cells have entries such as =2.872*10^-19 which display as 2.872E-19, it would appear you have real numbers and not text. A bit of a mystery! You have not set the y scale min & max to anything other than 'automatic' have you? Have you tried a new workbook entering values like this x y 1 1E-10 2 2E-10 3 3E-10 4 4E-10 can you get a chart with these values? By the way: if I was working with numbers like yours (but as a scientist I cannot think of anything that small that I could measure!) I would use x = 0.1111 y= 2.872 x = 0.0625 y= 4.043 x = 0.0400 y= 4.576 x = 0.0277 y= 4.814 Then I would scale the resulting slope and intercept by a factor of 10^-19 "Lala" wrote in message ... Yes the graph choosen is the xy scatter graph. The values I'm trying to graph are : x = 0.1111 y= 2.872*10^-19 ; (2.872E-19 when actually posting in the cell) x = 0.0625 y= 4.043*10^-19 ; (4.043E-19) x = 0.0400 y= 4.576*10^-19 ; (4.576E-19) x = 0.0277 y= 4.814*10^-19 ; (4.814E-19) Again the Y values of (1E-19 to 6E-19) are not posting, only 0 value is posting. When editing the y axis the minimum value on automatic is 0 and the maximum does say 6.0E-19. But on the actual agraph I don't see these values. So when doing a line graph I only get a linear equation of y=5E-19 instead of y=mx+b. Excel does graph the data points and when adding data labels, the values appear. It's just the division values (1.00E-19 to 6.00E-19) on the y axis that doesn't appear. I've also tried setting the cells to scientific numbers, general and numbers but that didn't help. It has to be the program because I've had 2 people graph my data and it worked on their software. |
#13
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Yes thank you, it is a software issue. I thought I was doing something wrong
/ human error in inputing data or formatting the graph. I hope this bug gets fixed because I'd rather not get another version of excel and I might need to graph data with numbers this small again. Anyway to get automatically notified should a patch for this bug gets issued? Thanks for all the responses/help. "Jon Peltier" wrote: Without doing anything special, I created a chart and added a trendline. It worked as expected, and I got this formula: y = -2.3507E-18x + 5.4943E-19 R2 = 9.9921E-01 This worked the same in Excel 2000 and in 2003. Then I tried it in Excel 2007 and it failed in the same manner that you described. The Y axis only showed 0.0000E00 at the bottom, and no more values, and the formula showed Y = 5.4943E-19, omitting the constant. Excel apparently thought this was a rounding error and coerced it to zero. I ran a set of trials where I multiplied the Y values of each trial by ten to get the Y values for the next. My regression formulas looked like: y = 5.49429E-19 [R² = 9.99213E-01] y = 5.49429E-18 [R² = 9.99213E-01] y = 5.49429E-17 [R² = 9.99213E-01] y = 5.49429E-16 [R² = 9.99213E-01] y = -2.35066E-14x [R² = 9.99213E-01] y = -2.35066E-13x + 5.49429E-14 [R² = 9.99213E-01] y = -2.35066E-12x + 5.49429E-13 [R² = 9.99213E-01] y = -2.35066E-11x + 5.49429E-12 [R² = 9.99213E-01] The first formula came from your example. Note that the constant has the same pre-exponential factor for all of the formulas (5.49429) except for the case when it would be 5.49429E-15, which sounds like a threshold for being considered a rounding error. In all cases where the coefficient of X wasn't ignored, the coefficient's pre-exponential factor was the same (-2.35066), and in all cases, R² was the same (0.999213). I repeated this in Excel 2003, and the formulas were identical except for the exponents of the fitting constants. I'd classify this one more as a bug than as a feature. - Jon ------- Jon Peltier, Microsoft Excel MVP Tutorials and Custom Solutions http://PeltierTech.com _______ "Lala" wrote in message ... Yes the graph choosen is the xy scatter graph. The values I'm trying to graph are : x = 0.1111 y= 2.872*10^-19 ; (2.872E-19 when actually posting in the cell) x = 0.0625 y= 4.043*10^-19 ; (4.043E-19) x = 0.0400 y= 4.576*10^-19 ; (4.576E-19) x = 0.0277 y= 4.814*10^-19 ; (4.814E-19) Again the Y values of (1E-19 to 6E-19) are not posting, only 0 value is posting. When editing the y axis the minimum value on automatic is 0 and the maximum does say 6.0E-19. But on the actual agraph I don't see these values. So when doing a line graph I only get a linear equation of y=5E-19 instead of y=mx+b. Excel does graph the data points and when adding data labels, the values appear. It's just the division values (1.00E-19 to 6.00E-19) on the y axis that doesn't appear. I've also tried setting the cells to scientific numbers, general and numbers but that didn't help. It has to be the program because I've had 2 people graph my data and it worked on their software. "Bernard Liengme" wrote: It would be helpful to see at least 5 data points (both the x and the y values): could you list them for us? Are you sure you have made an XY chart and not a Line chart? If you wish you may send me a file with the data best wishes -- Bernard V Liengme www.stfx.ca/people/bliengme remove caps from email "Lala" wrote in message ... I have the home and student 2007 version. When graphing a scatter graph with the Y axis having 10 to the negative power, excel doesn't show the values on the y axis. It only shows the 0 intercept value. I've tried editing the axis values but the number still doesn't display and excel automatically puts the number to at least 10 decimal places, ie 5.000000000000001E-19. When I just click automatic, the right values appear in the edit menu but the y values still won't show on the actual graph. So when doing a trendline the equation doesn't show an m slope value, ie y=5E-19. A friend graphed my data on an older version excel and it graphed it properly with the proper y values displaying, and linear trendline equation was in right format of y = mx + b, ie y= -2E-18x + 5E-19 Could my software be defective? Or are some features disabled? |
#14
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Posted to microsoft.public.excel.charting
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I am having a similar problem. I am using excel 2007 to make calibration
curves using scatter plots. When I add a linear trendline, the equation displayed is incorrect in 2007, however when plotted on an older version, the equation is correct. I have found a way to "circumvent" the problem, formatting the numbers in the lable to have decimals (2 places) the equation corrects itself, however, I am left with an R2 value with only 2 decimal places. I noticed this error after wasting a good days work using the wrong equations given in 2007!!!!! I too thought I was going nuts! The concentrations calculated from the equation was completely wrong from the concentrations obtained when extrapolating from the line!!!!! Microsoft needs to fix these problems fast!!!!!!!! "Lala" wrote: Yes thank you, it is a software issue. I thought I was doing something wrong / human error in inputing data or formatting the graph. I hope this bug gets fixed because I'd rather not get another version of excel and I might need to graph data with numbers this small again. Anyway to get automatically notified should a patch for this bug gets issued? Thanks for all the responses/help. "Jon Peltier" wrote: Without doing anything special, I created a chart and added a trendline. It worked as expected, and I got this formula: y = -2.3507E-18x + 5.4943E-19 R2 = 9.9921E-01 This worked the same in Excel 2000 and in 2003. Then I tried it in Excel 2007 and it failed in the same manner that you described. The Y axis only showed 0.0000E00 at the bottom, and no more values, and the formula showed Y = 5.4943E-19, omitting the constant. Excel apparently thought this was a rounding error and coerced it to zero. I ran a set of trials where I multiplied the Y values of each trial by ten to get the Y values for the next. My regression formulas looked like: y = 5.49429E-19 [R² = 9.99213E-01] y = 5.49429E-18 [R² = 9.99213E-01] y = 5.49429E-17 [R² = 9.99213E-01] y = 5.49429E-16 [R² = 9.99213E-01] y = -2.35066E-14x [R² = 9.99213E-01] y = -2.35066E-13x + 5.49429E-14 [R² = 9.99213E-01] y = -2.35066E-12x + 5.49429E-13 [R² = 9.99213E-01] y = -2.35066E-11x + 5.49429E-12 [R² = 9.99213E-01] The first formula came from your example. Note that the constant has the same pre-exponential factor for all of the formulas (5.49429) except for the case when it would be 5.49429E-15, which sounds like a threshold for being considered a rounding error. In all cases where the coefficient of X wasn't ignored, the coefficient's pre-exponential factor was the same (-2.35066), and in all cases, R² was the same (0.999213). I repeated this in Excel 2003, and the formulas were identical except for the exponents of the fitting constants. I'd classify this one more as a bug than as a feature. - Jon ------- Jon Peltier, Microsoft Excel MVP Tutorials and Custom Solutions http://PeltierTech.com _______ "Lala" wrote in message ... Yes the graph choosen is the xy scatter graph. The values I'm trying to graph are : x = 0.1111 y= 2.872*10^-19 ; (2.872E-19 when actually posting in the cell) x = 0.0625 y= 4.043*10^-19 ; (4.043E-19) x = 0.0400 y= 4.576*10^-19 ; (4.576E-19) x = 0.0277 y= 4.814*10^-19 ; (4.814E-19) Again the Y values of (1E-19 to 6E-19) are not posting, only 0 value is posting. When editing the y axis the minimum value on automatic is 0 and the maximum does say 6.0E-19. But on the actual agraph I don't see these values. So when doing a line graph I only get a linear equation of y=5E-19 instead of y=mx+b. Excel does graph the data points and when adding data labels, the values appear. It's just the division values (1.00E-19 to 6.00E-19) on the y axis that doesn't appear. I've also tried setting the cells to scientific numbers, general and numbers but that didn't help. It has to be the program because I've had 2 people graph my data and it worked on their software. "Bernard Liengme" wrote: It would be helpful to see at least 5 data points (both the x and the y values): could you list them for us? Are you sure you have made an XY chart and not a Line chart? If you wish you may send me a file with the data best wishes -- Bernard V Liengme www.stfx.ca/people/bliengme remove caps from email "Lala" wrote in message ... I have the home and student 2007 version. When graphing a scatter graph with the Y axis having 10 to the negative power, excel doesn't show the values on the y axis. It only shows the 0 intercept value. I've tried editing the axis values but the number still doesn't display and excel automatically puts the number to at least 10 decimal places, ie 5.000000000000001E-19. When I just click automatic, the right values appear in the edit menu but the y values still won't show on the actual graph. So when doing a trendline the equation doesn't show an m slope value, ie y=5E-19. A friend graphed my data on an older version excel and it graphed it properly with the proper y values displaying, and linear trendline equation was in right format of y = mx + b, ie y= -2E-18x + 5E-19 Could my software be defective? Or are some features disabled? |
#15
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Posted to microsoft.public.excel.charting
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I have noticed numerous axis labelling errors in the student version of Excel
2007; forced reformatting of number values being among them. Label rounding and placement errors also appear commonplace. Does Microsoft have any Excel 2007 fixes on the way? "Lala" wrote: I have the home and student 2007 version. When graphing a scatter graph with the Y axis having 10 to the negative power, excel doesn't show the values on the y axis. It only shows the 0 intercept value. I've tried editing the axis values but the number still doesn't display and excel automatically puts the number to at least 10 decimal places, ie 5.000000000000001E-19. When I just click automatic, the right values appear in the edit menu but the y values still won't show on the actual graph. So when doing a trendline the equation doesn't show an m slope value, ie y=5E-19. A friend graphed my data on an older version excel and it graphed it properly with the proper y values displaying, and linear trendline equation was in right format of y = mx + b, ie y= -2E-18x + 5E-19 Could my software be defective? Or are some features disabled? |
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