How to find tangent of a curve and find the distance from the centre?

I have plotted a curve from a jpg image using the ginput feature of matlab. It comes out to be a curve. I want to find the various radius of the curve at different points.I thought of finding the tangent at different point. But i dont know the curve equation, how to achieve this?

Answer 1

[Amit Bhowmick]

If you have xdata ydata get the equation of the curve using cfit tools.

[Rahul Seth]

Okay. Let me try it out and get back to you. Thank You for your reply.