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polyfit at 74 how can I improve results?

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RS
RS on 28 Aug 2013
Type of error coming how can I make good results warning(message('MATLAB:polyfit:RepeatedPoints'));
In polyfit at 74 Warning: Polynomial is badly conditioned. Add points with distinct X values or reduce the degree of the polynomial.
I am using this
[p S mu]= polyfit(x1(1:xxx),y2,3);

Answers (1)

Image Analyst
Image Analyst on 28 Aug 2013
Do you have some x1 values that are repeated? What does this say
length(unique(x1(1:xxx)) - length(x1(1:xxx)) % No semicolon
  3 Comments
Image Analyst
Image Analyst on 28 Aug 2013
Edited: Image Analyst on 28 Aug 2013
Can't be 1, must be -1 because you can never have more unique values than original values. So, this is as I thought. One of the x values is repeated, meaning that you have two different y values for the same x value and thus the "curve" would have to be perfectly vertical at that location. That is not allowed. Do something to resolve that "step" in your data and it should then be okay.
RS
RS on 28 Aug 2013
every time I am doing fitting it is not coming -1 how can I do? some time it is coming some positive numbers.

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