CODEWITHSUNDEEP
matlab
Kashif
Kashif

Reputation: 3327

how do I convert a string array to a numeric in matlab?

I have a cell array {'W','L','D','D','W'}. I want to convert this into a {-1,0,1} array where 'W' is mapped to 1, 'D' to 0, and 'L' to -1.

Is there a quick way to do this without writing a loop?

Upvotes: 1

Views: 147

Answers (3)

Edric
Edric

Reputation: 25140

You could use categorical arrays to do this in a single expression

double(categorical({'W','L','D','D','W'}, {'L', 'D', 'W'})) - 2

Or for MATLAB prior to R2013b, you can do two expressions:

[~, loc] = ismember({'W','L','D','D','W'}, {'L', 'D', 'W'});
result = loc - 2;

Upvotes: 6

zegkljan
zegkljan

Reputation: 8401

@GameOfThrows's answer is good but it would not generalize well should your character-number mapping become more complex. Here is my solution:

Create a function that maps the characters the way you want

function n = mapChar(c)
    if strcmp(c, 'W')
        n = 1;
    elseif strcmp(c, 'D')
        n = 0;
    elseif strcmp(c, 'L')
        n = -1;
    end
end

and then use cellfun to apply it over the cell array:

>> cellfun(@mapChar, {'W','L','D','D','W'})

ans =

     1    -1     0     0     1

If you find that you need to use a different mapping, you just redefine your mapping.

Also, it all can be inlined (using part of the @GameOfThrows's approach):

>> cellfun(@(c)(strcmp(c, 'W') - strcmp(c, 'L')), {'W','L','D','D','W'})

ans =

     1    -1     0     0     1

Upvotes: 0

GameOfThrows
GameOfThrows

Reputation: 4510

use strcmp :

A = {'W','L','D','D','W'};
B = strcmp (A,'W');
C = strcmp (A,'L') * -1;
B+C

ans =

 1    -1     0     0     1

Upvotes: 4

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