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Summing graphs without differnt independent variables
Hey all,
I am having a very inconvinient problem, which seems to potentially ruin several weeks of hard work -- and it would be immensly appreciated if anyone could come up with a quicly implementable solution. OK, the data I am trying to present is power demand for trains on a distance of rail over time. In the data I have, power demand is measured at every 250 metres for each train. This means taht my data is like this. m T1 T2 . . . 0 1500 5462 . . . 250 1700 1654 . . . 500 1200 6542 . . . 750 4000 1224 . . . 1000 3100 5555 . . . .. .. .. Where at each cell (each 250 m) I know the power demand. Additionally, I know at what time the trains passed each 250-metre point. Therefore, with graph with a X-Y Scatter Chart, I can graph Power as a function of time even though time is not an independent variable. However, I have problems graphing the aggregate power demand as a function of time. Is there anyway I can sum alle the graphs in one chart, or anything similar? Thanks in advance |
Summing graphs without differnt independent variables
Thanks Jon!
Yeah, this was what I figured. But this will make the results a lot less exact, because the curve is -- and thus the parts of the curve between each point are -- not linear. Is there no way Excel can interpolate directly from the chart, and hence expand the data to contain a value for every point of time? "Jon Peltier" wrote: You want to sum demand at each time? you need to have a value at each time for each series. This means you need to somehow interpolate all curves to a standard set of time points, then add these interpolated values. - Jon ------- Jon Peltier, Microsoft Excel MVP Tutorials and Custom Solutions Peltier Technical Services, Inc. - http://PeltierTech.com _______ "Sebastian Stormbo" <Sebastian wrote in message ... Hey all, I am having a very inconvinient problem, which seems to potentially ruin several weeks of hard work -- and it would be immensly appreciated if anyone could come up with a quicly implementable solution. OK, the data I am trying to present is power demand for trains on a distance of rail over time. In the data I have, power demand is measured at every 250 metres for each train. This means taht my data is like this. m T1 T2 . . . 0 1500 5462 . . . 250 1700 1654 . . . 500 1200 6542 . . . 750 4000 1224 . . . 1000 3100 5555 . . . . . . Where at each cell (each 250 m) I know the power demand. Additionally, I know at what time the trains passed each 250-metre point. Therefore, with graph with a X-Y Scatter Chart, I can graph Power as a function of time even though time is not an independent variable. However, I have problems graphing the aggregate power demand as a function of time. Is there anyway I can sum alle the graphs in one chart, or anything similar? Thanks in advance |
Summing graphs without differnt independent variables
Interpolation is a non-trivial area, see
http://en.wikipedia.org/wiki/Interpolate You ask Excel to interpolate between values, but say linear interpolation is inappropriate without indicating what form of interpolation might be OK. I think your choices a a) use linear interpolation and hope it's close enough; depends on the form of the relationship and the spacing of the points; perhaps transform your data so the relationship is more like linear, try log(Power)?. b) fit a curvilinear regression model ; if you know the (approximate) form of the relationship and can fit it, see LINEST, GROWTH, LOGEST, TREND c) learn a bit more about interpolation; I don't think Excel has many (any?) means of interpolation built-in in an easy to use form But I'm not an Excel expert, just a lurking statistician. HTH A Lurker "Sebastian Stormbo" wrote in message ... Thanks Jon! Yeah, this was what I figured. But this will make the results a lot less exact, because the curve is -- and thus the parts of the curve between each point are -- not linear. Is there no way Excel can interpolate directly from the chart, and hence expand the data to contain a value for every point of time? "Jon Peltier" wrote: You want to sum demand at each time? you need to have a value at each time for each series. This means you need to somehow interpolate all curves to a standard set of time points, then add these interpolated values. - Jon ------- Jon Peltier, Microsoft Excel MVP Tutorials and Custom Solutions Peltier Technical Services, Inc. - http://PeltierTech.com _______ "Sebastian Stormbo" <Sebastian wrote in message ... Hey all, I am having a very inconvinient problem, which seems to potentially ruin several weeks of hard work -- and it would be immensly appreciated if anyone could come up with a quicly implementable solution. OK, the data I am trying to present is power demand for trains on a distance of rail over time. In the data I have, power demand is measured at every 250 metres for each train. This means taht my data is like this. m T1 T2 . . . 0 1500 5462 . . . 250 1700 1654 . . . 500 1200 6542 . . . 750 4000 1224 . . . 1000 3100 5555 . . . . . . Where at each cell (each 250 m) I know the power demand. Additionally, I know at what time the trains passed each 250-metre point. Therefore, with graph with a X-Y Scatter Chart, I can graph Power as a function of time even though time is not an independent variable. However, I have problems graphing the aggregate power demand as a function of time. Is there anyway I can sum alle the graphs in one chart, or anything similar? Thanks in advance |
Summing graphs without differnt independent variables
I would not pretend that the smoothed line option of a series formatting
produces accurate values between actual points. You certainly don't want a software package to make assumptions about your data in any case. You could try to fit a polynomial (please limit the degree you use, no more than second order) or another relationship which is physically meaningful to your model. - Jon ------- Jon Peltier, Microsoft Excel MVP Tutorials and Custom Solutions Peltier Technical Services, Inc. - http://PeltierTech.com _______ "Sebastian Stormbo" wrote in message ... Thanks Jon! Yeah, this was what I figured. But this will make the results a lot less exact, because the curve is -- and thus the parts of the curve between each point are -- not linear. Is there no way Excel can interpolate directly from the chart, and hence expand the data to contain a value for every point of time? "Jon Peltier" wrote: You want to sum demand at each time? you need to have a value at each time for each series. This means you need to somehow interpolate all curves to a standard set of time points, then add these interpolated values. - Jon ------- Jon Peltier, Microsoft Excel MVP Tutorials and Custom Solutions Peltier Technical Services, Inc. - http://PeltierTech.com _______ "Sebastian Stormbo" <Sebastian wrote in message ... Hey all, I am having a very inconvinient problem, which seems to potentially ruin several weeks of hard work -- and it would be immensly appreciated if anyone could come up with a quicly implementable solution. OK, the data I am trying to present is power demand for trains on a distance of rail over time. In the data I have, power demand is measured at every 250 metres for each train. This means taht my data is like this. m T1 T2 . . . 0 1500 5462 . . . 250 1700 1654 . . . 500 1200 6542 . . . 750 4000 1224 . . . 1000 3100 5555 . . . . . . Where at each cell (each 250 m) I know the power demand. Additionally, I know at what time the trains passed each 250-metre point. Therefore, with graph with a X-Y Scatter Chart, I can graph Power as a function of time even though time is not an independent variable. However, I have problems graphing the aggregate power demand as a function of time. Is there anyway I can sum alle the graphs in one chart, or anything similar? Thanks in advance |
Summing graphs without differnt independent variables
On Fri, 18 Jul 2008, in microsoft.public.excel.charting,
Sebastian Stormbo said: Yeah, this was what I figured. But this will make the results a lot less exact, because the curve is -- and thus the parts of the curve between each point are -- not linear. Is there no way Excel can interpolate directly from the chart, and hence expand the data to contain a value for every point of time? Why should charts be any better at knowing where the curves go than spreadsheet cells? Computing is computing. -- Del Cotter NB Personal replies to this post will send email to , which goes to a spam folder-- please send your email to del3 instead. |
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