Linear fit (What is the standard error)

Hi, all,

I make a linear fit for my data.

% linear fit
P = polyfit(x,y,1);
yfit = P(1)*x+P(2);

I can find the zero by taking the division of -P(2)/P(1). My question is, what is the standard error for the -P(2)/P(1) I find? What is the matlab code for this?

[Chan]

I have found the solution. It's rather straightforward.

[P,S,mu] = polyfit(y,x,1); % has to flip the position of x and y

[y_center,error] = polyval(P,0,S,mu);