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how to replace elements in top third, middle third, and bottom third of matix

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My task is the following:
Write a function called trio that takes two positive integer inputs n and m. The function returns a 3n-by-m matrix called T. The top third of T (an n by m submatrix) is all 1s, the middle third is all 2-s while the bottom third is all 3-s. See example below:
M = trio(2,4)
M =
1 1 1 1
1 1 1 1
2 2 2 2
2 2 2 2
3 3 3 3
3 3 3 3
This is the code that I wrote, but it only works for T = trio (4,3). I want my code to work for any input of n,m.
function T = trio (n, m)
T = randi (10, (3 * n) , m);
T ( 1:n , :) = 1;
T ( (n+1):(end-(n-1)) , :) = 2;
T ( (n+3):end, :) = 3;
end
How is it possible to call out only top third, middle third, and bottom third of any matrix?
Thank you in advance.

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Accepted Answer

James Tursa
James Tursa on 1 May 2019
Edited: James Tursa on 1 May 2019
Your row indexing is wrong.
The first n rows are 1:n which you have correct.
The second n rows indexing is n more that the first set, so simply add n: n + (1:n)
The third n rows indexing is n more than the second set, which I will let you figure out (it's pretty simple)

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Marlon Izaguirre
Marlon Izaguirre on 1 May 2019
Thank you so much James!!!! I was able to figure out the third n rows.
I really appriciate your time.

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More Answers (9)

AYUSH GURTU
AYUSH GURTU on 28 May 2019
function T = trio (n, m)
T = randi (10, (3 * n) , m);
T (1:n,:) = 1;
T ((n+(1:n)),:) = 2;
T (n+(n+(1:n)):end,:) = 3;
end

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mayank ghugretkar
mayank ghugretkar on 5 Jun 2019
function T=trio(n,m)
T(3*n,m)=3; % or you can use random no. generation...but since we are assigning alues anyway , this vl work fine !
T(1:n,:)=1;
T((n+1):2*n,:)=2;
T((2*n+1):3*n,:)=3;
end
hope this'll help, welcome !

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Nijita Kesavan Namboothiri
function T = trio (n, m)
T = randi (10, (3 * n) , m);
T ( 1:n , :) = 1;
T ( (n+1):(2*n) , :) = 2;
T ( ((2*n)+1):end, :) = 3;
end

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Doga Savas
Doga Savas on 22 Aug 2019
function d = trio(n,m)
a = randi(1,n,m);
b = 2 + rand(n,m)*0;
c = 3 + rand(n,m)*0;
d = [a;b;c];
end

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Yihan Liu
Yihan Liu on 23 Sep 2019
Edited: Yihan Liu on 23 Sep 2019
function T= trio(n,m)
T = randi (10, n, m);
T(:) = 1;
T1 = T;
T(:) = 2;
T2 = T;
T(:) = 3;
T3 = T;
T = [T1;T2;T3];
end

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Sowmya Allani
Sowmya Allani on 24 Sep 2019
function T=trio(n,m)
T=randi(3,3*n,m)
[n,m]=size(T)
x=n/3;
T(1:x,:)=1;
T(x+1:x*2,:)=2;
T((x*2)+1:x*3,:)=3;
end

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evan muas
evan muas on 2 Dec 2019
function T=trio(n,m)
T=[ones(n,m);2*ones(n,m);3*ones(n,m)]
end

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Akash Devalekar
Akash Devalekar on 16 Dec 2019
function T=trio(n,m)
w=ones(n,m);
y=ones(n,m)+1;
x=ones(n,m)+2;
T=[w;y;x];
end

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