I have a number of data points that appear to fit a negative
exponential model. When I graph the data in Excel that is how it
looks. However, the trends that Excel allows do not appear to fit
negative functions. Can someone tell me how to modify the trend
fitting capability of Excel to handle this data.

Please post detailed steps. I am looking a cancer data that I need to
model and display.

Thanks,

oldman

Did you try to fit an exponential trendline to the data? The icon shows
exponential growth but the formula can just as well be fitted to exponential
decay.


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-------
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wrote in message
...
I have a number of data points that appear to fit a negative
exponential model. When I graph the data in Excel that is how it
looks. However, the trends that Excel allows do not appear to fit
negative functions. Can someone tell me how to modify the trend
fitting capability of Excel to handle this data.

Please post detailed steps. I am looking a cancer data that I need to
model and display.

Thanks,

oldman

Excel 2007
http://en.wikipedia.org/wiki/Biological_half-life
....isotope decays perfectly according to first order kinetics ... a
living organism follows more complex kinetics....
I suspect that you are seeing a second order rate equation curve.
Here is a comparison:
http://www.mediafire.com/file/uzuizg...06_12_09a.xlsx

Thanks for the response. It has been more than 20 years since I
worked with this stuff. What I am attempting to model the effect on
cancerous plasma cells of the drug Cytoxan. The patient has Multiple
Myeloma and has under gone two transplants and a stem cell boost. The
patient had relapsed again I is under going a new chemo regimen of
Dex, Velcade and Cytoxan. We so far have five sample points of 8.58,
5.80, 2.04, 1.42 and 1.28. The data looks like it is a decaying
exponential. The last two points have brought the patient into the
normal range but now appear to be tapering off. Each sample point is
the cancer marker for that week.

I can not seem to get the screen shot for function argument.

Though at this point there is not sufficient data to model this
situation I believe I am on the right track. I have never worked with
this capability it Excel so the reason for the post.


Hopefully, you can give me more help with how to use this capability
in Excel.

Thanks,
oldman


On Fri, 12 Jun 2009 19:34:19 -0700 (PDT), Herbert Seidenberg
wrote:

Excel 2007
http://en.wikipedia.org/wiki/Biological_half-life
...isotope decays perfectly according to first order kinetics ... a
living organism follows more complex kinetics....
I suspect that you are seeing a second order rate equation curve.
Here is a comparison:
http://www.mediafire.com/file/uzuizg...06_12_09a.xlsx

On Sat, 13 Jun 2009 13:25:56 -0700, wrote:


Though at this point there is not sufficient data to model this
situation I believe I am on the right track. I have never worked with
this capability it Excel so the reason for the post.


List a set of numbers for an axis. List more. List them all! :-)


Let me play with the data, then you can label them however you like.

Also if you see it (one of my solutions)the way you want it, you would
see the chart characteristics as well,and be able to use it in the
future..

Hi thanks for the response. I will display what data I have which are
the first five points for the last five weeks of data since the chemo
protocol changed.

Week Kappa freelites
0 8.58
1 5.80
2 2.04
3 1.42
4 1.28
5 1.15
6 1.05
7 .99
8 .89
9 .81
10 .78


This should be enough of a start. The normal range if the disease is
under control is .33 to 1.94. These drugs are not a cure but only a
means to keep things under control. This is the sixth treatment plan
she has tried since being diagnosed almost five years ago.

Again we really appreciate the help.

oldman










On Sat, 13 Jun 2009 13:46:53 -0700, TheQuickBrownFox
wrote:

On Sat, 13 Jun 2009 13:25:56 -0700, wrote:


Though at this point there is not sufficient data to model this
situation I believe I am on the right track. I have never worked with
this capability it Excel so the reason for the post.


List a set of numbers for an axis. List more. List them all! :-)


Let me play with the data, then you can label them however you like.

Also if you see it (one of my solutions)the way you want it, you would
see the chart characteristics as well,and be able to use it in the
future..

On Sat, 13 Jun 2009 14:27:13 -0700, wrote:

Hi thanks for the response. I will display what data I have which are
the first five points for the last five weeks of data since the chemo
protocol changed.

Week Kappa freelites
0 8.58
1 5.80
2 2.04
3 1.42
4 1.28
5 1.15
6 1.05
7 .99
8 .89
9 .81
10 .78


This should be enough of a start. The normal range if the disease is
under control is .33 to 1.94. These drugs are not a cure but only a
means to keep things under control. This is the sixth treatment plan
she has tried since being diagnosed almost five years ago.

Again we really appreciate the help.

oldman

Where are the negative exponents?

Excel 2007
Inserted your data into my tables.
A second order rate equation with offset
still gives the best fit.
See Sheet2/Chart2.
http://www.mediafire.com/file/kn4jey...06_12_09b.xlsx

Hi oldman,

I'd be happy to help you fit a trendline to your negative exponential data in Excel. Here are the steps you can follow:

1. First, enter your data into Excel. Make sure you have two columns: one for the x-values (usually time or some other independent variable) and one for the y-values (the dependent variable you want to model).
2. Select your data and create a scatter plot. To do this, go to the Insert tab and select Scatter from the Charts section. Choose the type of scatter plot you want (e.g. with or without markers).
3. Right-click on one of the data points in your chart and select Add Trendline. This will open the Format Trendline pane on the right side of the screen.
4. In the Format Trendline pane, select the Options tab. Under Trendline Name, choose Exponential.
5. Under Trendline Options, check the box for Display Equation on chart. This will show you the equation for the trendline.
6. If you want to adjust the appearance of the trendline, you can do so under the Line Style and Line Color sections of the Format Trendline pane.

That's it! Your chart should now have a trendline that fits your negative exponential data. If you want to make sure the trendline is a good fit, you can also add R-squared and/or adjusted R-squared values to your chart. To do this, go to the Chart Elements button on the right side of the chart and select More Options. Check the boxes for R-squared and/or adjusted R-squared.