How can I get the average of curves on a plot?

Hello!

I would like to get the average curve from several curves on a plot. Is there a way to do this in Excel?

(Background infromation: I have, say, 10 sets of XY points and I want to take the average of these to obtain a set of average X and Y points and plot them. However, each of these 10 sets have a different amount of XY points and I can't simply take the average across the row. Any solutions?)

Thanks!

(A) If the X-values are the same for each series the Y-value of the average
is simply the average of the respective y-values.
(B) So, I assume yr X-values are not equal, though within a comparable
scale. You cld try to interpolate / extrapolate the xy-pairs to obtain a
kind of best-fit curve, with Add Trendline you can choose a polynomial fit
which gives you say 10 estimated curves. Now the one y'r looking for is the
average of Y-values belonging to that fit, identical as in (A).
HTH,
Henk

"jessie joe" wrote:

>
> Hello!
>
> I would like to get the average curve from several curves on a plot. Is
> there a way to do this in Excel?
>
> (Background infromation: I have, say, 10 sets of XY points and I want
> to take the average of these to obtain a set of average X and Y points
> and plot them. However, each of these 10 sets have a different amount
> of XY points and I can't simply take the average across the row. Any
> solutions?)
>
> Thanks!
>
>
> --
> jessie joe
> ------------------------------------------------------------------------
> jessie joe's Profile: http://www.excelforum.com/member.php...o&userid=36054
> View this thread: http://www.excelforum.com/showthread...hreadid=558432
>
>

I am not sure I understand. How do I get the set of average X and Y values from the 10 estimated curves?

1) Fit each of the 10 data sets to a suitable curve (polynomial or other). Use LINEST or chart trendlines.
2) You can then take an average of the 10 curves by selecting a value for x, calculating the value for y at each of the 10 curves, then average that set of y's. This will give you an average value for y at a given x. Repeat for as many x's as needed.

If your data is noisy, then fitting a polynomial (as others suggested) can
smooth it before you average. However, if the data is not noisy and not from
a low order polynomial, you should be aware that a least squares fit need not
pass through any observed points.

If you really want to average what the chart displays, then the chart
smoother appears to fit Bezier curves

http://www.xlrotor.com/Smooth_curve_...ample_file.zip

which in most instances is not greatly different than cubic splines

http://groups.google.com/group/micro...2966520eccdb1f

(local polynomial fits that do pass through the data points, as opposed to a
global polynomial fit that may not).

Jerry

"jessie joe" wrote:

>
> Hello!
>
> I would like to get the average curve from several curves on a plot. Is
> there a way to do this in Excel?
>
> (Background infromation: I have, say, 10 sets of XY points and I want
> to take the average of these to obtain a set of average X and Y points
> and plot them. However, each of these 10 sets have a different amount
> of XY points and I can't simply take the average across the row. Any
> solutions?)
>
> Thanks!
>
>
> --
> jessie joe
> ------------------------------------------------------------------------
> jessie joe's Profile: http://www.excelforum.com/member.php...o&userid=36054
> View this thread: http://www.excelforum.com/showthread...hreadid=558432
>
>