fitlm works but polyfit does not work

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alpedhuez
alpedhuez 2020-12-6
评论： Ameer Hamza 2020-12-6
I run polyfit and fitlm for the same data. fitlm provides an output. But polyfit and corrcoef return NaN. How can it be?

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Ameer Hamza
Ameer Hamza 2020-12-6
编辑：Ameer Hamza 2020-12-6
There is probably NaN somewhere in your dataset. fitlm() ignores those data values. For example
x = linspace(0, 1, 10);
y = 2*x + 3 + rand(size(x));
y(3) = nan;
p = polyfit(x, y, 1)
c = corrcoef(y)
ft = fitlm(x, y)
Result
>> p
p =
NaN NaN
>> c
c =
NaN
>> ft
ft =
Linear regression model:
y ~ 1 + x1
Estimated Coefficients:
Estimate SE tStat pValue
________ _______ ______ __________
(Intercept) 3.1773 0.13254 23.973 5.5901e-08
x1 2.3847 0.21348 11.17 1.0268e-05
Number of observations: 9, Error degrees of freedom: 7
Root Mean Squared Error: 0.206
R-squared: 0.947, Adjusted R-Squared: 0.939
F-statistic vs. constant model: 125, p-value = 1.03e-05

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