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# To get a random number

Asked by Muruganandham Subramanian on 18 Jan 2012

Hi,

`   Am having a incremental column matrix like, e.g. for 1st iteration, it is 100*1(double), then for 2nd iteration iteration, it will be 100*2(double), etc.. Form this, for 1st iteration, i need to get a random no (single data only). from 1st column of matrix  and for 2nd iteration, i have to get a random no. from 2nd column of matrix only.`
`              Thank you in advance!!@!!`

## 1 Comment

Michael on 18 Jan 2012

Maybe I misunderstand but to me this question appears contradictory. How is a number random if it depends on your column as an input?

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Answer by Wayne King on 18 Jan 2012

You can use

```x = randperm(100);
randomindex = x(1);
```

Then, use that index to choose an element from the appropriate column, say your data matrix is X

```X(randomindex,1)  %choose from first column
X(randomindex,2)  %choose from 2nd column
```

Muruganandham Subramanian on 20 Jan 2012

Hi walter,
It's not working.
am having both negative and non-negative integers of 100*1, In this i have to pick single data randomly.

Walter Roberson on 20 Jan 2012

Sorry, the references to size(X,2) should have been size(X,1)

rchoices = randperm(size(X,1));
randchoice = X(rchoices(1),IterationNumber);

Muruganandham Subramanian on 20 Jan 2012

It's working...
Thanks walter