Help with Basic Matrix Exercise

Hi :) I'm learning Matlab by myself with some tutorial that i found online. I know, I'm a newbie but i can't solve this exercise. Could someone help me? Should be very easy cause i found this in a starter course.

Create a 6(rows)x4(columns) matrix filled with random integer values between 1 and 20; Create a zeroes matrix of the same dimensions; Replace each zero with a random number from the other matrix; Display each value in the new mixed matrix

Thank you :)

Answer 1

[Andreas Goser]

To get you started, check

doc rand
doc zeros

Probably this is the easy part. If you get to "Replace each zero with a random number from the other matrix;", you may want to share all the code you have to that time in a new question here with your specific struggle (if any).

[Nicholas Menghi]

Thank you for your answer, this is what I did:

mat1 = (rand(6, 4))
mat2= zeros(6,4)

for i= [1,1]:length(mat1)
    for k = [1,1]:size(mat1)
    mat2(i) = mat1(i)
    mat2(k) = mat1(k)
    end
end
disp(mat1)
disp(mat2)

But Random number are not integer and i can replace only the first column.

[Stephen23]

"But Random number are not integer": Here are three very easy ways you can locate the correct way to generate random integers:

• use any internet search engine.
• open the rand page, and browse the Contents on the left-hand-side.
• open the rand page and click on the links at the very bottom of the page (to related functions).

If you had done any of these things you would immediately find out that there is a function for generating random integers, and rand is not it.

The indexing problem you would also solve in 0.5 seconds using any internet search engine. But here it is, just in case you don't have that much time:

mat2(row,col) % how to index rows and columns

http://www.mathworks.com/help/matlab/math/matrix-indexing.html

http://www.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html

[Nicholas Menghi]

Ok, now I'm stuck here

mat1 = randi(20,6,4)
mat2 = zeros(6,4)

for i= [(1:6),(1:1)]
    for k = [(1:1)]:[(1:4)]
    mat2(i) = mat1(i)
    mat2(k) = mat1(k)
    end
end
disp(mat1)
disp(mat2)

I don't know, it changes again only the first column... 0.5... secs now I am feeling a little wretched.