Asked by Lalit Patil
on 21 Jan 2013

polyfit(x,y,1)

How to implement the same thing without function..?

*No products are associated with this question.*

Answer by Jan Simon
on 21 Jan 2013

I assume that this is a homework question. There are good reasons to look for a faster implementation than Matlab's `polyfit`, but you do not ask for speed.

At first you need to construct the Vandermonde matrix. There are a lot of different algorithms to get it, and Google or WikiPedia know more details.

At second the least squares problem must be solved. `V \ y` with the Vandermonde matrix V and the y values is sufficient. A QR decomposition is more stable, so I suggest to try it and ask again in case or problems.

Be sure to use properly scaled inputs for x: A mean of 0 and a standard deviation of 1 is a fair choice to support the numerical stability of the algorithm. It is easy to consider the scaling afterwards.

MATLAB and Simulink resources for Arduino, LEGO, and Raspberry Pi test

Learn moreOpportunities for recent engineering grads.

Apply Today
## 0 Comments