1 Topic by ali_fz (edited by ali_fz 2013-10-24 17:05:45)

Topic: High order Polynomial Trend line

Hi

Dear Ivan; Today I observed an strange error while try to draw a polynomial trend line in Graph.
I check it in other PC and the error occurred again.

I think it is not a bug and only accumulation of the errors of calculation result this wrong output.
Any way I attached a grf file with  2 series of point (8 point in one seri and 12 point in other one)I try to find a 7-order polynomial for it  (7~11 for the other one) .

http://up.ht/1fVxWHG

when you use trend line dialog and do it; you will see that a good trend line is drawn. But save your action and close the file and open it again. (or open the property dialog box of the current trend line and change color or any value of it (refreshing))

You will see that the function is not a trend line and has moved far from points!



I would like to know more about this strange action.

Also have a question:
If there is a way to have the splines function or evaluated table of a spline series?

Thanks

Re: High order Polynomial Trend line

What happens is that Graph generates a function from your points and plots that. But when the function is saved as a grf file or edited, a text representation of the function is created. This only uses 6 decimals for number, which apparently is not enough in your case. As there is no need to limit the number of decimals I have now increased it to 12 in the beta version:
http://padowan.dk/graph/DownloadBeta.php

Re: High order Polynomial Trend line

thank you so much. I got it. smile