Why is polyfit giving me "NAN"

Hello,
I am curious why polyfit is returning 'nan'. My data set is finite and positive. I am attempting to study a power function and use it for my data. so here is what I have:
p = polyfit(log(x), log(y), 1);
However, I keep getting:
p = [nan nan] The dimensions of x and y are 1 column and 2617 rows
Please help and thank you so much!!

4 commentaires

dpb
dpb le 30 Juin 2016
Range issue w/ log, most likely?
What is min(log()) and max for x, y?
You can try the scaling option to see if helps the numerics...
W/o a dataset, tough to say much more than "that's what the data say", sorry.
Walter Roberson
Walter Roberson le 30 Juin 2016
Do you possibly have duplicate x ?
Image Analyst
Image Analyst le 30 Juin 2016
Does x or y have 0, or negative numbers, or nan's in them?
Samuel Vergara
Samuel Vergara le 30 Juin 2016
I think you have zeros in X or Y. so log(0)=-inf. Try with cftool.
Regards.

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