how to detect all local minima in radon transform and average distance between them?

I want to detect motion blur parameters in image using radon transform.

im= imread ('blurredimage.tif');
Rd=radon(log(abs(fft2(diff(im)))));
mx=max(Rd(:));
(Row column)=find(mx==Rd)

Here column gives blur angle theta i.e. blur direction.

I got stuck in computing blur length,

Blur length is computed by finding avg dist of local minima in radon transform.

[Walter Roberson]

Duplicates http://uk.mathworks.com/matlabcentral/answers/231372-how-to-detect-all-local-minima-in-radon-transform-and-average-distance-between-them