Vectorize Radon transform eqn

The Radon transform eqn is given as

where

P is projection data

 f(x,y) is  the grayscale image

delta is dirac delta function

theta is fs:fs:360

without vectorization it includes 4 loops for r, theta, x and y

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for a 255x255 image my code is

fs=30;

theta=fs:fs:360;

rad=deg2rad(theta);

x=flipud((-127:127)');

y=-127:127;

t=x;

P(t,1:length(theta))=integral2(img*dirac(cos(rad).*x+sin(rad).*y-t),-127,127,-127,127);

but this code is giving dimensions missmatch