Thanks for help I will try it.

I am sorry for the mistake, How I can know the goodness of my fitting?and what is equation which Maple usually use to calculate the standared deviation of the fitting parameters and the residual mean square, the residual standard deviation and the residual sum of squre.please see the file.Thanks Download 6828_Maple-test.txt
View file details Download 6828_Maple-test-Nl.mws
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