how to output how many numbers in the range are prime numbers using the function that i created?

function[ result ] = MyPrime( X );

this is my function how do i input an array to the input argument which is X and output how many prime numbers are there in the range and list them? thanks I am new to MATLAB

[Stephen23]

What you have written is not a function because it does not start with the function operator. It is actually a script. You can read about the different between scripts and functions in the documentation. One MATLAB M-file can contain either

1. one script
2. one or more functions

It is not possible to mix the two: a file either is a script, or has functions, but cannot have both. I would recommend that you learn to write code using functions, which have many advantages over scripts.

Answer 1

[Thorsten]

I have correct the code and made several remarks; if you call the function without argument X, the user is asked to input the range. Then the user has to type the brackets [ ] around the input, like [10 20].

function theprimes = MyPrime( X ) % use keyword function to define a function
% rename results to theprimes

if nargin == 0 % user input of range if no argument is supplied to function
  X = input('Enter a range of numbers: ');
end

m = 1;
theprimes = []; % initialize return value
for i = X(1):X(end) % :1: is the default, not necessary, and ; is not needed here
  %k=mod(i,1:i);
  %zero=find(k==0);
  %n_zero=length(zero);
  %if n_zero==2  % no ; needed here

    % instead of the above 4 lines, you could also use the nnz function and no extra variables
    if nnz(mod(i,1:i) == 0) == 2
      theprimes(m)=i; % use function return value theprimes here
      m=m+1;
    end
    % i=i+1; % that's wrong, i is incremented in the for loop already
  end

c=numel(theprimes);
if c == 0 % NOT theprimes==0; if isempty(theprimes) would also work
  fprintf('There are no prime numbers\n')
else
  fprintf('There are %0.d prime numbers and they are ', c);
  fprintf(' %d',theprimes) % use theprimes, not c
end

Answer 2

[Stalin Samuel]

Check this

[Natalia Wong]

i am not allowed to use isprime i have already created my own function to determine prime number

[Bjorn Gustavsson]

Well the problem you have is twofold.

1, you have not written a function MyPrime since you seem to have put that code in the script task2.m, the function-file should start with a line:

function [res] = MyPrime(X)

which should be followed by the code in your script where you check whether the number is a prime. 2, Then you'll have to clean up the script.