MATLAB: A better explanation of polyfit please

polyfit

My teacher wants us to use polyfit and gave us a little bit of information on how to use it, but what he gave us makes no sense and I've looked on this website for an explanation and that didn't help me. I know that the form is polyfit(x,y,n) but I'm not sure what the n stands for or how to figure it out from a set of data. Thanks in advance.

Best Answer

The ‘n’ is the degree of the polynomial. The degree can be considered to be the highest power of the independent variable, x. So a first-degree polynomial is p(1)*x + p(2), a second-degree p(1)*x^2 + p(2)*x + p(3), and so forth.

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MATLAB: Correlation between two row matrices

Like that, each value of "a" is correlated to each value of "b", but applying the formula of the correlation, the correlation of two single numbers is NaN. To compute the correlation correctly, traspose the input vectors

result  = corr(a', b');

MATLAB: Same matrix but not equal problem

When you see something that you do not understand, LOOK AT YOUR DATA.

C(1,:)
ans =
  Columns 1 through 31
   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN
  Columns 32 through 45
   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN
C1(1,:)
ans =
  Columns 1 through 31
   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN
  Columns 32 through 45
   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN
isequal(NaN,NaN)
ans =
  logical
   0
NaN == NaN
ans =
  logical
   0

NaNs are not equal to NaNs.

nnz(isnan(C))
ans =
      543150
numel(C)
ans =
      995220

Roughly half of your array elements are NaN.

You can test for equality, where NaNs are considered to be equal to NaNs, using isequaln.

isequaln(C,C1)
ans =
  logical
   1

Best Answer

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MATLAB: Correlation between two row matrices

MATLAB: Same matrix but not equal problem

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