Script that performs the same as MATLAB function.

I am looking to create scripts for some internal functions: repmat, fliplr, flipud, and rot90. I am familiar with how each works but I am not sure where I should start. I have two of the four below.

%This script will perform the same operation as rot90
x = input('Enter the matrix: ');
[m,n] = size(x);
[i,j] = length(x);
y = input('Which direction to rotate the matrix\nEnter -90 or 90: ');
newvec = 0; %This is the variable for the result
if y == -90
    %rotate counterclockwise
elseif y == 90
   %rotate clockwise
end

%This script will duplicate the user entered matrix and create a new matrix
%by the number of rows and columns specfied by the user. 

mat = input('Enter your matrix: \n');
rows = input('Enter number of rows: \n');
cols = input('Enter number of columns: \n');
newvec = zeros(rows,cols,mat);

[Walter Roberson]

newvec = zeros(rows,cols,mat); is going to be rejected unless mat is entered as a scalar by the user.

[Walter Roberson]

It is not clear what you are asking? What assistance are you hoping for from us?

If you are looking for information on the algorithm to implement these functions: figuring that out is most of the work of the homework assignment.

Hint: look at "for" loops.

[David Hughes]

I rewrote the rot90 script using a for loop but I am not getting the rotation, swapping columns for rows and vice versa. I am unsure how to swap the rows for columns in the direction specified by user.

x = input('Enter the matrix: ');
y = input('Which direction to rotate the matrix\nEnter -90 or 90: ');
[m,n] = size(x);
rows = 0;
cols = 0;

for i = 1:m
    for j = 1:n
       if y == -90
          x(i) = x(j) %rotate counterclockwise
       elseif y == 90
          x(j) = x(i) %rotate clockwise
       end
    end
end

[David Hughes]

This is what I got for rotating 90 degrees.

%This script will perform the same operation as rot90
clc
clear all
mat = input('Enter the matrix: ');
drctn = input('Which direction to rotate the matrix\nEnter -90 or 90: ');
[m,n] = size(mat);
fprintf('You entered\n')
disp(mat)
for i = 1:m
        if drctn == 90  %Rotate clockwise
            mat90(:,i) = mat(m-i+1,:);
        elseif drctn == -90  %Rotate counter clockwise
            mat90(i,:)= mat(:,m-i+1);
        end
end
fprintf('The result is\n')
disp(mat90)

[Walter Roberson]

Are you getting an error message with that second script?

[David Hughes]

The second script, to perform like repmat, does give an error.

[Steven Lord]

And the full text of the error message you receive from your repmat-like script is ... ?

[BTW, I'm assuming you're doing this for homework. If not, I recommend you simply use the functions included with MATLAB.]

[David Hughes]

Yes this is an assignment. The error I was getting was from some changes I made. I've gone back to the beginning and made some additions. I realized I needed to allocate the memory for the resulting matrix. Not getting an error but I am stuck. I am getting the correct size of the resulting matrix but not the correct values. I know that adding i + j in the nested for-loop is not the correct syntax for the correct result. I added i + j as a test and this is where I am stuck.

clear all
clc
mat = input('Enter your matrix: ');
rows = input('Enter number of rows: ');
cols = input('Enter number of columns: ');
[m,n] = size(mat);
newvec = zeros(rows*m,cols*n);

for i = 1:size(newvec)
    for j = 1:size(newvec)
        newvec2(i,j) = i + j;
    end
end
disp(newvec2)