Here’s a useful little script I wrote in IDL. It allows you to send it 2 arrays (x and y data) and then you can plot the data, and fit it with a Hubble profile:
y = I * (1 + x/r_c)^(-a)
where I, r_c and a are constants representing the vertical scaling, the core radius and the exponent of decline, respectively.
It’s interactive, and allows you to adjust parameters and re-fit on the fly.
Click here to download it.