I am trying to fit a curve to a number of pixels in an image so I can do further processing regarding it's shape. Does anyone know how to implement a least squares method in C/++ preferably using the following parameters: an x array, a y array, and an answers array (the length of the answers array should tell how many coefficients need to be calculated)?
If this is not some exercise in implementing this yourself, I would suggest you use a ready-made library like GNU gsl. Have a look at the functions whose names start with gsl_multifit_, see e.g. the second example here.