We have points x(i),y(i),s(i), where i=1,....,N and s(i) is the standard deviation ("error bar") of y(i).

This is a Fortran 90 line-fitting program [linefit.f90]

 Intercept and expected error :  0.22112252494404125 0.009332726022970368
 Slope and expected error     :  0.5506251596885045 0.002800789912660865
 Number of data points        :  51
 X2 per degree of freedom     :  1.170613622829978

The data was generated by adding noise (distributed according to Gaussians with mean 0 and variable width equal to the stated errors) to a line y=a+bx with a=0.23 and b=0.55. These parameters are seen to be reproduced by the fitting program to within statistical errors.