Error Marix dimensions must agree.

I am attempting to run this simulation 100,000 times to get an average amount of turns that can be played before the player loses the game. However after i inserted my for loop i received an error stating

Matrix dimensions must agree.

Error in untitled (line 36) if color == 'red'

if i remove the for loop the program runs fine but i need the while loop to iterate 100000 times.

any help would be much appreciated.

%General Housekeeping
clear all

clc

money=100;
bet=10;
color=input('Place your bet on red or black: ','s');

j=0;
sum=0;

for ii = 1:100000
    
    i=0;
    
    while money >= 0
        r=randi([0 36]);

        if r == 0
            fprintf('The ball lands on green.\nYou lose your bet.\n\n')
            money=money-bet;
        elseif mod(r,2) == 0
            if color == 'red'
                fprintf('The ball lands on %g which is black.\nYou lose.\n\n',r);
                money=money-bet;
            elseif color == 'black'
                fprintf('The ball lands on %g which is black.\nYou win.\n\n',r);
                money=money+bet;
            end
        else
            if color == 'red'
                fprintf('The ball lands on %g which is red.\nYou win.\n',r);
                money=money+bet;
            elseif color == 'black'
                fprintf('The ball lands on %g which is black.\nYou lose.\n',r);
                money=money-bet;
            end
        end

        i=i+1;
    end
    
    sum=sum+i;
    j=j+1;
end
        
average=sum/j;

Answer 1

[Walter Roberson]

input() with the 's' option returns a character vector. Character vectors are vectors of characters, where characters are effectively uint16() -- numbers really. So when you use == between a character vector and a constant, you are doing a vector comparison, same as if you had asked

if [114 101 100] == [98 108 97 99 107]  %if 'red' == 'black'

which of course is a matrix dimension mismatch.

You need to use strcmp() or strcmpi(), or else you need to switch to using string() objects -- the == operator for string objects does do string comparison.

if 'red' == "black"                     %double quotes make it a string object