polynomials fitting

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SAM alimostafa
SAM alimostafa on 25 May 2011
hi if i want to use polyfit and polyval for two vectores x and y do they must be at the same size?? in my case x is greater than y by one and i want to predict the value of y at that point wt can i do????

Accepted Answer

Ben Mitch
Ben Mitch on 25 May 2011
say you have
x = [1 2 3 4];
y = [8 12 16];
then you can fit a polynomial to the region you have data for (the first three samples) using
p = polyfit(x(1:length(y)), y, 1);
and estimate all the samples using
y_est = polyval(p, x);
or just the ones you don't have data for using
y_est = polyval(p, x(length(y)+1:end));

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