Making a Matrix calculator

I would like to make a calculator that would ask the user for the number of matrices involved, and then add, subtract, divide, or multiply said matrices. After some digging around, I think I could use while loops, and some switch/case loops to pull this off. I am wondering if this would be the best way to approach this, or if there were some other loops I might not have considered that could help me out. Any advice or suggestions would be appreciated.

[dpb]

Whatever you do, do NOT create the input arrays as sequentially-numbered variables like M1, M2, ..., etc.

Use structures or cell arrays or other higher abstraction data that can be manipulated without having to resort to evil eval

It's unfortunate that Mathworks didn't let plus, + have a variable number of arguments; then one could just call it with a list, but it and its brethren are limited to two arguments only.

[Stephen23]

I don‘t see why you would need any WHILE loops for this: a cell array and FOR loops would likely be sufficient.

[Ray]

@dpb Thank you for this advice. I am planning to use a cell array, something akin to matrices = cell(1, numMatrices);

I plan on initializing a zero matrix, that can then be populated with matrix elements from the user

[Ray]

@Stephen23 I plan on using the while loops for if the user inputs something invalid. I want to give the user a chance to correct their mistake without re-running the code. Like if the user put -1 for the number of rows/columns for example.

[dpb]

@Ray, a nicety would be to allow a user a list of indices and values -- like eye(3) is only three nonzero elements whereas the full array would require entering all nine.

[Stephen23]

"I plan on using the while loops for if the user inputs something invalid"

https://www.mathworks.com/help/matlab/ref/uitable.html

[Ray]

@Stephen23 Thank you for that link. I would like to try to add a UI later.

[Ray]

@dpb as tedious as it would be, I would like the user to input all the elments.

[Ray]

@dpb @Stephen23

Thank you both, I have a fundamentally working program! I can post it if either of you are interested in critiquing me.

Answer 1

[Prasanna]

For Matrix Calculator, try this IF ELSE Case.

Take this example. It might be helpful for you.

a = input('Enter First Matrix: ');
b = input('Enter Second Matrix: ');
out = input('Operation to do: '); % ADD = 1/SUBTRACT = 2/MULTIPLY = 3/DIVIDE = 4
if out == 1 
    output_add = a+b
elseif out == 2
    output_subtract = a-b
elseif out == 3
    output_product = a*b
elseif out == 4
    output_divide = a/b
else
    fprintf('No proper input')
end

Answer 2

[Umeshraja]

Hello @Ray,

If you’re just starting out with MATLAB and want a solid foundation, I recommend first completing the MATLAB Onramp course. It offers a great introduction to MATLAB basics and will help you feel more comfortable working with the environment.

To help build your matrix calculator, here are some useful resources to guide you:

• The official documentation on the 'input' function explains how to ask users for input and perform validation to ensure the data entered is correct.
• https://www.mathworks.com/help/matlab/ref/input.html?requestedDomain=
• For a clear overview of fundamental matrix operations such as addition, subtraction, and multiplication, refer to the MATLAB guide on matrix operations.
• https://www.mathworks.com/help/matlabmobile/ug/matrix-operations.html
• To understand the differences between element-wise operations and matrix operations (for example, the distinction between * and .*), check the page comparing array and matrix arithmetic.
• https://www.mathworks.com/help/matlab/matlab_prog/array-vs-matrix-operations.html
• Lastly, there is a resource detailing all matrix arithmetic operators and how to use them properly.
• https://www.mathworks.com/help/simulink/matrix-operations.html
• Additionally, if you want to learn about element-wise multiplication
• https://www.mathworks.com/help/matlab/ref/double.times.html

Hope this helps!

Answer 3

[ali]

can we change it a little bit. you can totally build your matrix calculator without drowning in while-loops and switch-cases. The big thing is: don’t make variables like M1, M2, M3…Just throw all your matrices into a cell array and loop through them — way cleaner and way less headache.

Use a while loop only when the user screws up the input, like entering -1 for rows. That’s fine. But for the actual matrix operations, a simple for-loop is all you need.

So the flow is basically: ask how many matrices they want, store them in a cell array, then run whatever operation they chose across that list. MATLAB doesn’t let you do multi-argument A + B + C + D, so you just start with the first matrix and keep stacking the operations in a loop.

Here:

result = matrices{1};

for i = 2:numMatrices

result = result + matrices{i}; % or -, *, /

end