Line fitting in Matlab

I've been using this for several times but I always forget where I put the source code, so every time I have to rewrite it again. So, I think it would be better if I put the source code here so it will be easier for me to find if I need this again.

This is almost the same with the article that I wrote using GSL, I use Matlab because I need to show the 3D, I haven't finished my 3D visualization software yet.

So here we go:

- Assume that you have a line data, Y(1:540) which are changing with the X value, X(1:540).

- Then basically, you just have to call this polynomial fitting function in Matlab: p = polyfit(X,Y,n);

- The result from this function is an array p which has n+1 element and representing the coefficient of the polynomial equation p1*x^(n) + p2*x^(n-1) + ... + p(n+1). for example if n = 1, then the equation will be p(1).x - y2 + p(2) = 0.

- To generate the line, simply plot the equation to the X value, for example:

for col=1:1:540

y2(col) = p(1)*x(col) + p(2);

end

plot(x, y, x, y2);

- To get the difference between the line and the actual values, the distance from point to a line formula can be used.

for col=1:1:540

d(col) = (p(1)*x(col) - Y(col) + p(2)) / sqrt( (p(1)*p(1))+1 );

end

- Then you can show the deviation in another figure.

Hope it helps.

Good luck.

writing a well-written code is faster than debugging a badly written code...

Debugging is a pain in the ass..
It can make you sleepless in the evening, lose your mood in the morning, decrease your appetite, and even a nightmare, hahaha...

Lesson learned: It's better to write a well-written code than you have to spend time in debugging your code in the end.. Sometimes, after you wrote the code, you don't even remember why you wrote it that way. This is what makes debugging a difficult job.

This is the most efficient way to develop a software, trust me hehe..