Making Matrices with Loops

This is the assignment I was given:

Create a script called script19.m. The script should assume scalar value of n is assigned in the command window. The script should create an n-by-n matrix A where

A = [nn ... n2 n1;
     ....

       2n ... 22 21;

       1n ... 12 11]

An example execution is as follows:

>> n = 3;
>> script19
A =
    33 32 31
    23 22 21
    13 12 11

This is the script I wrote but I still can't get an answer:

A = zeros(N);

for ii = N : 1
    for jj = (10*ii) + N : (10* ii) + 1
        A = jj
    end
end

Am I on the right track??

Answer 1

[the cyclist]

You are on the right track. I can give you a couple hints:

First, be aware that the loop

for ii = N : 1

won't work. I think you want

for ii = N : -1 : 1

so that ii counts down. Similarly for your other loop.

Next, notice that inside your loop, you are not writing to specific positions in your A matrix. You'll need to fix that.

Answer 2

[Walter Roberson]

A = [10*(1:n)', ones(n,1)] * [ones(1,n);1:n];

[Gina Barlage]

this needs to go from the higher number to the lower number down and across. I tried A = [10*(N: -1:1)', ones (N,1) * [ones(1.N); 1:N] and it kept giving me an error.

[Thorsten]

 A = [10*(n:-1:1)', ones(n,1)] * [ones(1,n);n:-1:1];

Answer 3

[Andrei Bobrov]

bsxfun(@minus,((10*n+n):-10:10)',0:n-1)