Writing a function to count the number of times a word pops up in a random word generation.

I'm trying to write a function that

1. Generates iterations times a random word of length size;
2. Check for each of them whether the input name appears in the generated random word, using the function I made - mychartrec;
3. Counts the number of successes, i.e., the number of times the answer is YES in the previous experiment.

My function mychartrec is

function [result] = mychartrec(x, y)
n = length(x);
m = length(y);
if n > m
    [result] = false;
    return
else
    for k = 1:m-n+1
        if mychartest(x, y(k:k+n-1))
            [result] = true;
            return
        end
    end
end
end

and what I've got for the function I'm trying to create is

function result = iamrandom(size, iterations, name)
result = 0;
alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
r = randi(26, iterations, size);
words = alphabet(r);
disp(words)
for i = 1:iterations
    word = words(i);
    if mychartrec(name, word) == true
        result = result + 1;
        disp(word)
    end
end
end

but whenever I run the function, it always produces a result of 0, even if the word generated includes the name within. I'm trying to do this without using strings.

[Rik]

You're only selecting a single letter. If you use the debugger to step through the code, you can see the state of all variables at each step.

I would also suggest using cellstr. It will allow you to use ismember, without sacrificing any compatibility.

[Emily Newton]

okay so, is it only selecting thr first letter of the first word? or the first letter of each word?

and i cant use any string functions, as im working on my loops, so im trying to use the other function i created

Answer 1

[Voss]

Consider the difference between the following two pieces of code.

First, set up the variables for both:

number_of_words = 5;
word_length = 7;

alphabet = 'A':'Z';
r = randi(numel(alphabet), number_of_words, word_length);
words = alphabet(r);
disp(words)

MNKKNGN
EJDPAAP
SGQEQXE
LKTIGSS
NBJOPEB

1) Using words(i):

for i = 1:number_of_words
    word = words(i)
end

word = 'M'

word = 'E'

word = 'S'

word = 'L'

word = 'N'

2) Using words(i,:):

for i = 1:number_of_words
    word = words(i,:)
end

word = 'MNKKNGN'

word = 'EJDPAAP'

word = 'SGQEQXE'

word = 'LKTIGSS'

word = 'NBJOPEB'

words is a 2d character array, and words(i) is the ith element of words - a single character, just as the ith element of a numeric matrix is a single number:

A = magic(3)

A = 3×3

8 1 6 3 5 7 4 9 2

A(2)

ans = 3

Alternatively, words(i,:) gives you the ith row of words, just as A(i,:) gives you the ith row of the numeric matrix A:

A(2,:)

ans = 1×3

3 5 7

[Emily Newton]

ive made it so the for loops goes

for i = 1:iterations

word = words (i, :)

if mychartrec(name, word) == 1

result = result + 1

end

end

but i keep getting the error message 'output argument not assigned durimg call to "mychartrec",

do you know whats causing this?

[Voss]

In mychartrec, reproduced here

function [result] = mychartrec(x, y)
n = length(x);
m = length(y);
if n > m
    [result] = false;
    return
else
    for k = 1:m-n+1
        if mychartest(x, y(k:k+n-1))
            [result] = true;
            return
        end
    end
end
end

if n <= m (so that the else block executes) but mychartest(x, y(k:k+n-1)) is never true for any k, then the variable result is not defined. That is, result is only defined when there is a match (in which case it is true) or when n > m (in which case there can be no match and it is false). It remains undefined in the case that there could be a match according to the word lengths but there is no match in fact.

You have to make sure result is defined in every possible case, so something like this would work:

function result = mychartrec(x, y)
n = length(x);
m = length(y);
if n > m
    result = false;
    return
else
    for k = 1:m-n+1
        if mychartest(x, y(k:k+n-1))
            result = true;
            return
        end
    end
    % if we're here, then the k loop ran and didn't find any match,
    % so result is false
    result = false;
end
end

[Voss]

However, I would simplify that function a bit. Recognizing that a for loop given an empty array executes zero times, you don't have to have a special case for when n > m. You can merely initialize result to be false, then if you find a match, set result to true and return:

function result = mychartrec(x, y)
n = length(x);
m = length(y);
result = false;
for k = 1:m-n+1
    if mychartest(x, y(k:k+n-1))
        result = true;
        return
    end
end
end

Note that, in case n > m, the loop executes zero times, and result remains false as it should be.