Finding values in a matrix for a given range

Example:

I have a vector k =[1 2 3 4 5 6 7 8 9] and a range = [2 3 4] The values corresponding to the range is given by k=k(range) = 2 3 4

Does anyone know how to code it when k and range is matrices?

[Walter Roberson]

Is the question to find the indices within k at which the values in "range" are matched? Or is the question to generalize subscripting to the situation where matrices are involved instead of just vectors?

Answer 1

[Laura Proctor]

If your range is always going to be a consecutive range of values, then you can try:

k = 1:9;
r = 2:4;

k = k(k>=min(r) & k<=max(r))

If you want to compare each value of r against each value of k, then this would work:

iVals = logical(zeros(size(k)));
for idx = 1:length(r)
    iVals = iVals | k==r(idx)
end

k = k(iVals)

This assumes that r is a vector.

[Walter Roberson]

If r is going to be a consecutive increasing range of values, then min(r) and max(r) have predictable locations:

k = k(k>=r(1) & k<=r(end))

[Laura Proctor]

Jannie - could you clarify? I'm answering the question as if range is the range of numbers that you wish to find in k, whereas it could also be interpreted to be the range of index values.

Answer 2

[Walter Roberson]

What would your range represent when you are using matrices? Would it be row indices, column indices, or indices in to the entire matrix?

For some of the possibilities, k(range) would still work.

Answer 3

[Andrei Bobrov]

example:

 >> k = randi(35,7)
  k =
       6    33    24     2    34    18    23
      34    28    27    10     2    16     6
      34    34    27     2    16    23     5
      17    23    14     4    14    25    18
      29     2    23    29    27    27    34
       5    30     6    25    28    10    12
      15    33    25    12     7    24    21
  >> range = randi([1 numel(k)],3)
  range =
      11    25    48
      37    35    27
      13    44     7
  >> k(range)
  ans =
      23     4    12
      16     7    25
      30     6    15
  >>