I want to create a random matrix?

Help me!

I want to create a random matrix HM (3,5), it satisfies the following conditions:

1. The value of HM is a nonnegative integer from 0 to 4.

2. The total value of the elements in a row is less than or equal to 5.

Thank you very much!

[Wayne King]

0 is not a positive integer. And why a nonnegative integer from 0 to 4? How can you select a 4 and possibly get a sum less than or equal to 3?

[Pham]

Ok, sorry. a nonnegative integer from 0 to 4 with the total value of the elements in a row is less than or equal to 6.

[Pham]

you can help me

Answer 1

[Amit]

okay .. an approach would be rejection method .. be careful .. for extremely large matrix this will be a bad idea .. tmp1= randi([0 c],a*100,b); tmp1=tmp1(sum(tmp1,2)<=d); HM=tmp1(1:a,:);

[Amit]

the idea here is to create a large matrix(that's why 100*a) and the reject the values which don't qualify the conditions ..

[Pham]

When I for example: a = 5, b = 8, c = 4, d = 8, the matrix size is HM (5,1)?

[Amit]

you can also use while loop as well for rejection method, but that will be slower..

[Amit]

correction: tmp1=tmp1(sum(tmp1,2)<=d,:)

[Pham]

OK. Thanh you very much!

[Pham]

Hello

The code above has the following disadvantages: When b is large and d is small, the matrix tmp1 to satisfy the conditions will be the number of rows <a. So HM matrix will fail. For example:

tmp1= randi([0 3],5*10000,50);

tmp1=tmp1(sum(tmp1,2)<=10,:);

HM=tmp1(1:5,:)

It will error: Index exceeds matrix dimensions.

Are you using the loop, you can just help me. Thanks.

Answer 2

[Amit]

write down all possible ways to get 3 or less than 3 using integers 0-4 like [1 0 0 0 0] [1 1 0 0 0] etc.... pick one of the matrix for each row (randomly) and then use randperm to reorder them.

[Amit]

lets say you get 20 possible matrixes stored in comb(20,5) then:

temp1 = randi (20,10,1); HM=comb(temp1,:); for I=1:10 HM(I,:)=HM(I,randperm(5)); end

Sorry, I couldn't change it to code tags as I was replying from phone.

[Pham]

You can write a script to perform this matrix with a nonnegative integer from 0 to 4 with the total value of the elements in a row is less than or equal to 6.

[Pham]

Undefined variable comb.

Error in Untitled2 (line 2)

HM=comb(temp1,:);

[Amit]

comb is the matrix you'll make. comb in your case will be [1 0 0 0 0; 1 1 0 0 0; 1 1 1 0 0;2 0 0 0 0; 2 1 0 0 0;3 0 0 0 0]

[Pham]

Thank you, but it looks like this is complex and crafts. You can just give me the brief command to create this matrix.

[Amit]

the final code for your case:

comb=[1 0 0 0 0;1 1 0 0 0;1 1 1 0 0;2 0 0 0 0;2 1 0 0 0;3 0 0 0 0]; temp1 = randi (6,10,1); HM=comb(temp1,:); for I=1:10 HM(I,:)=HM(I,randperm(5)); end

[Pham]

You have way without using comb because the matrix HM large size, you can not list all cases of comb.

[Amit]

you changed the question from original post and how is 3×5 matrix matrix huge? and to make comb matrix, just make a code based on how you'll do it if you were suppose to do this on paper.

[Pham]

Because the matrix in my program HM large size. I just gave an example of a small matrix HM with such constraints.

[Amit]

Then can you state your real problem please?

[Pham]

I want to create a random matrix HM (a,b), it satisfies the following conditions:

1. The value of HM is a nonnegative integer from 0 to c.

2. The total value of the elements in a row is less than or equal to d.

Above example is only one case.

Can you help me. Thank you very much!

[Amit]

does b, c and d have any correlation? like in the example case, you have b=c+1, d=c+1

[Pham]

b, c and d are any integers