matlab - Find Value at a given Orientation in Matrix -

in matlab i've matrix where, in previous stage of code, specific element chosen. point of matrix find maximum, not maximum value between surounding neighbours given radius, maximum value @ given angle of orientation. let me explain example:

this matrix a:

a =

 0     1     1     1     0     0     9     1     0       0     2     2     4     3     2     8     1     0       0     2     2     3     3     2     2     1     0       0     1     1     3     2     2     2     1     0       0     8     2     3     3     2     7     2     1      0     1     1     2     3     2     3     2     1      

the element chosen in first stage 4 in a(2,4), , next element should maximum value with, example, 315 degrees angle of orientation, 7 in a(5,7).

what i've done is, depending on angle, subdivide matrix in different quadrants , make new matrix (an a's submatrix) values of quadrant.

so, example, submatrix a's 4th quadrant:

q_a =

 4     3     2     8     1     0       3     3     2     2     1     0       3     2     2     2     1     0       3     3     2     7     2     1       2     3     2     3     2     1      

and now, here question, how can extract 7?

the thing i've been able (and works) find values on threshold value , calculate how points orientated. then, saving values have similar orientation given 1 (315 degrees in example) , finding maximum among them. works guess there faster , "cleaner" solution.

this theory, don't have image processing toolbox test it. maybe can comment?

%make (r,c) center padding zeros     if r > size(a,1)/2         @ = padarray(a, [size(a,1) - r], 0, 'pre');     else         @ = padarray(a, [r-1], 0 'post');      if c > size(a,2)/2         @ = padarray(at, [size(a,2) - c], 0, 'pre');     else         @ = padarray(at, [c-1], 0 'post');  %rotate angle (maybe should -angle or else 360-angle or 2*pi-angle, i'm not sure     ar = imrotate(at,angle, 'nearest', 'loose'); %though think nearest , loose defaults  %find max      max(ar(size(ar,1)/2, size(ar,2)/2:end); %obviously must adjust handle case of odd dimension sizes. 

also depending on array requirements, padding -inf might better 0