How do I replace a value in a matrix at a certain point?

I'm trying to identify where the certain character is in my matrix and replace that character based on user input at that location. I cannot figure out a command that will work but this is what I have so far.

move = input('Your move?(a,w,d,q)','s');

switch (move)

    case 'a'
       find(world == 'v')
       [r,c] = find(world == 'v')
       for world = 'v'
          world(r,c) = '>'
       end
       for world = '^'
          world(r,c) = '<'
       end
       for world = '<'
          world(r,c) = 'v'
       end
       for world = '>'
          world(r,c) = '^'
       end

Answer 1

[Guillaume]

I'm afraid the code you show makes no sense at all.

To find something in a matrix, you indeed use find. Once you've found where it is, it's a simple matter of indexing to put a new value there

idx = find(m == searchvalue); %don't use [r,c] if there's going to be more than one found value
m(idx) = newvalue;

Maybe, what you're trying to do is this?

idx = find(world == 'v');
switch(move)
  case 'a'
    world(idx) = '<';
  case 'w'
    world(idx) = '^';
  case 's'
    world(idx) = 'v';
  case 'd'
    world(idx) = '>';
end

[Stephen23]

A faster (and often neater) alternative to find is to simply to use logical indexing .