find nearest value on matrix

find nearest value on matrix

Can someone help with this problem please..... for example a= 1250

matrix_b=[98 125 945 1005; 105 204 1105 1249; 200 250 1299 1450; 300 450 1350 1850]

want to find nearest equal or greater than a=1250 and the answer should be 1299

Answer 1

[Roger Stafford]

   result = min(b(b>=1250));

For this to work, there has to be at least one element of b that is greater than or equal to 1250.

[Image Analyst]

Or, using the poster's names for variables:

closestValue = min(matrix_b(matrix_b >= a));

Answer 2

[Walter Roberson]

   v = sort(matrix_b(:));
   vidx = floor(interp1(v, 1:length(v), a, 'linear', 'extrap'));
   if vidx ~= 0
      result = v(vidx);
   end

Or

   v = sort(matrix_b(:));
   vidx = find(v >= a, 1, 'first');
   if ~isempty(vidx)
     result = v(vidx);
   end

or

   v = sort(matrix_b(:));
   [~, vidx] = histc(a, v);
   if vidx ~= 0
     result = v(vidx);
   end

The middle of these is probably the easiest to think about, but it cannot be generalized to a list of a values like the other ones can (aside from the testing to be sure that a result was found.)

[Walter Roberson]

If you have R2016a or later, then

v = sort(matrix_b(:));
result = interp1(v, v, a, 'previous');

[FSh]

none of them works

[Walter Roberson]

The first of them did have a mistake, which I have now corrected.

Could you give an example that fails for the others?

[Walter Roberson]

Another approach:

v(interp1(v,1:length(v), a, 'nearest', 'extrap'))