Hello, is there any way I can define a matrix NxN whose elements are different real numbers between 0 and 5?

Hello, is there any way I can define a matrix NxN whose elements are different real numbers between 0 and 5?

Answer 1

[Taufik Sutanto]

Simply

rand(N)*5

will do ...

[jimaras]

thank you

[jimaras]

what about if I want to create a NxN matrix (1<N<2002) with random real number between 1 and 5 and the columns 1 and 2002 and the rows 1 and 2002 to be 0 ?

Answer 2

[Youssef Khmou]

try :

N=300;
M=5*rand(N);

[jimaras]

thank you

[jimaras]

what about if I want to create a NxN matrix (1<N<2002) with random real number between 1 and 5 and the columns 1 and 2002 and the rows 1 and 2002 to be 0 ?

Answer 3

[Azzi Abdelmalek]

N=5
out=reshape(linspace(0,5,N*N),N,N)

[jimaras]

what about if I want to create a NxN matrix (1<N<2002) with random real number between 0 and 5 and the columns 1 and 2002 and the rows 1 and 2002 to be 0 ?

[Azzi Abdelmalek]

M=rand(N)*5
M(randi(N*N))=0
M(randi(N*N))=5

Answer 4

[Image Analyst]

In your comments, you specified both 0 and 1 as the lowest value, so I made it flexible enough to handle either one:

N = 10; % Whatever you want
lowestValue = 1; % or 0 - whichever you want.
highestValue = 5;
theMatrix = lowestValue + (highestValue - lowestValue) * rand(N)
% Zero out first and last rows.
theMatrix(1,:) = 0;
theMatrix(end,:) = 0;
% Zero out first and last columns.
theMatrix(:,1) = 0;
theMatrix(:,end) = 0;

[jimaras]

very useful but I think I can never take the value of 5. Is this correct?

[Image Analyst]

Correct. Or zero, or any other number. The chance of getting any particular number EXACTLY is vanishingly small. For example, you'll most likely never hit 4.8 or 2.4 or 1.3 exactly either. If you're interested in integers, then use randi() instead of rand(). What exactly are you using this for anyway? Is it important that you get exactly 5 sometimes? If so, you're going to have to quantize your results, like round to the nearest 0.1 or something.

[jimaras]

I want to create two NxN matrices whose values can be between 0 and 5. I want later to implement these matrices in a prey & predator model so I think it's important to have values of 0 and of 5.

[Image Analyst]

Like I said in the code, just change lowestValue:

lowestValue = 0;

What about the requirement that the outer edges of the array be zero? Recall where you said "the columns 1 and 2002 and the rows 1 and 2002 to be 0 " - to me, that means that column 1 and column 2002 (or the last column if N is different that 2002) should equal exactly 0. And the same for the first and last row - they are all zero. Again, is this still required? If not, just don't do the zeroing out and do:

N = 2002; % Whatever you want
lowestValue = 0; % or 1 - whichever you want.
highestValue = 5;
theMatrix = lowestValue + (highestValue - lowestValue) * rand(N)

Essentially (in an inflexible, hard coded manner):

theMatrix = 5 * rand(2002)

Did you follow what I said in my prior comment about never being able to hit any particular number exactly ?