I have to run a regression of order 5. My X matrix is

` 102.1750 108.0515 102.1785 100.9413 102.6634`

My Y matrix is

` 0 5.4810 7.6267 24.7082 7.7284`

Both X and Y are approxiately 20×1, I just wanted to give an idea how they look like.

I have tried the following:

`1. Beta=pinv(X'*X)*(X'*Y);2. Beta=(X'*X)\(X'*Y);3. Beta=(X*Y);4. Beta=polyfit(X,Y,5); Expected=polyval(Beta,X);`

The results are very different. Additionally polyfit/polyval shows the following warning:"Warning: Polynomial is not unique; degree >= number of data points"

Any ideas or suggestions of what am I doing wrong or how or what else can I try? What is the correct way to do it?

## Best Answer