|
 Logarithmic and Exponential Trendlines |
| Posted by Scott on Mar-20-2009 14:26 |
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Hi,
I think this should be in the docs, but I can't seem to find it.
What are the exact equations resulting from exponential and logarithmic trendlines and what are the the indexes for their parameters from TrendLayer.GetCoefficient(i)?
-Scott |
| Re: Logarithmic and Exponential Trendlines |
| Posted by Peter Kwan on Mar-21-2009 01:53 |
|
Hi Scott,
You may go to the documentation on "TrendLayer" for details. (In the TrendLayer.GetCoefficient documentation, there should be a link to TrendLayer. You may also look for "TrendLayer" in the documentation index.)
In short, the formula for exponential regression is:
y = a0 * exp(a1 * x)
The formula for log regression is:
y = a0 + a1 * log(x)
The coefficient 0 (as obtained using getCoefficient) refers to a0, and the coefficient 1 is a1.
Hope this can help.
Regards
Peter Kwan |
| Re: Logarithmic and Exponential Trendlines |
| Posted by Scott on Mar-21-2009 02:48 |
|
Maybe I am doing something wrong, but the exponential equation generated using getcoefficient doesn't seem to match what is drawn by Chart Director.
The "exp(x)" function returns "e^x", correct? |
| Re: Logarithmic and Exponential Trendlines |
| Posted by Peter Kwan on Mar-21-2009 03:23 |
|
Hi Scott,
Sorry. I found out the documentation is wrong. The exponential formula is:
y = exp(a0 + a1 * x)
Hope this can help.
Regards
Peter Kwan |
| Re: Logarithmic and Exponential Trendlines |
| Posted by Scott on Mar-21-2009 03:36 |
|
Ah, that works.
Thank you. |
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