How to write a function.

Write a function called hw4_problem1 takes an at most two-dimensional matrix A as

its only input. The function returns a row vector v containing all elements of A that are prime

numbers. The elements of v are stored according to row-major ordering of A, which means you have

to check the elements in A row by row. You are allowed to use the isprime built-in function.

Hint: You can initialize the output v with an empty matrix before starting a loop, i.e., v = [];. As

you want to add more values to v, you can use end+1 as the new index in v. For example, if you

want to add a value 10 to the empty v, you can write v(end+1) = 10;. The variable v now has

one value, v(1) = 10;

Example run on Command Window:

>> v = hw4_problem1([ 38 83 24 54 6; 89 8 27 28 23])

v =

83 89 23

[Peyton]

function score = hw4_problem5(key, answers)
    % Check if both inputs are row vectors of the same length
    if ~isrow(key) || ~isrow(answers)
        score = -1; % Return -1 if either input is not a row vector
        return;
    elseif length(key) ~= length(answers)
        score = -1; % Return -1 if the lengths do not match
        return;
    else
        % Compute the score by comparing key and answers element-wise
        score = sum(key == answers); % Count the number of correct answers
    end
end

[Walter Roberson]

You describe hw4_problem1 but you post code for hw4_problem5

[Peyton]

i did lol im so tired but here is the correct one

function output = hw4_problem1(A, n)
    % Check if the input A is a numeric matrix
    if ~isnumeric(A)
        error('Input A must be a numeric matrix.');
    end

    % Check if the matrix A is empty
    if isempty(A)
        error('Input A cannot be empty.');
    end
    
    % Get the number of rows and columns of A
    [numRows, numCols] = size(A);
    
    % Output matrix for storing results (just as an example here)
    output = zeros(numRows, numCols);
    
    % Loop over the rows of A
    for i = 1:numRows
        for j = 1:numCols
            % Example operation: simply copy the elements of A to output
            output(i = 1:numRows, j = 1:numCols) = A(2,2);
        end
    end
end

[Walter Roberson]

output(i = 1:numRows, j = 1:numCols) = A(2,2);

In MATLAB, that would be equivalent to

output("i", 1:numRows, "j", 1:numCols) = A(2,2);

which would fail because strings such as "i" cannot be used as indexes into arrays.

Answer 1

[Madheswaran]

Hi @Peyton, This seems like a homework question, so I will give you a headstart, from which you can pick up. Learn how to write and call functions from here: https://mathworks.com/help/matlab/functions.html

Then, go through the following documentation and work on how to apply it to your question:

1. Note the input argument for the 'isprime' function - https://mathworks.com/help/matlab/ref/isprime.html
2. Learn what logical indexing is - https://mathworks.com/matlabcentral/answers/422002

Here is where you can learn more about MATLAB: https://matlabacademy.mathworks.com/details/matlab-onramp/gettingstarted

Hope this helps!