MATLAB Central Newsreader - Randomization_same number

Randomization_same number

Kostas — Fri, 06 Nov 2009 21:26:02 -0500

Hi all,

I am trying to present 4 different numbers 120 times in a vector, in a randomized order. But the thing is that I try to avoid repeating the same number twice in a row, and in the same time to keep the repetition frequency of each number the same (= 30).

Do you have any ideas?

Thanks

Re: Randomization_same number

Luigi Giaccari — Fri, 06 Nov 2009 21:58:02 -0500

"Kostas " <eclipse_dsotm@hotmail.com> wrote in message <hd249a$im2$1@fred.mathworks.com>...
> Hi all,
>
> I am trying to present 4 different numbers 120 times in a vector, in a randomized order. But the thing is that I try to avoid repeating the same number twice in a row, and in the same time to keep the repetition frequency of each number the same (= 30).
>
> Do you have any ideas?
>
> Thanks

BUild the 120 element vector in a sorted order than use "randperm"

The "randperm" will help you, but you need to postprocess the data to change duplicate values on a single row. A swap should be good.

http://www.advancedmcode.org/

Re: Randomization_same number

Kostas — Fri, 06 Nov 2009 22:10:03 -0500

>BUild the 120 element vector in a sorted order than use "randperm"
>
>The "randperm" will help you, but you need to postprocess the data to change duplicate >values on a single row. A swap should be good.
>
>http://www.advancedmcode.org/

Thanks for your reply. I think I should have mentioned that I must generate this vector a lot of times in the future, so it must me always different. :)

Thanks again

Re: Randomization_same number

John D'Errico — Fri, 06 Nov 2009 23:04:01 -0500

"Kostas " <eclipse_dsotm@hotmail.com> wrote in message <hd26rr$q78$1@fred.mathworks.com>...
> >BUild the 120 element vector in a sorted order than use "randperm"
> >
> >The "randperm" will help you, but you need to postprocess the data to change duplicate >values on a single row. A swap should be good.
> >
> >http://www.advancedmcode.org/
>
>
> Thanks for your reply. I think I should have mentioned that I must generate this vector a lot of times in the future, so it must me always different. :)
>
> Thanks again

So? Then be efficient in your code. Randperm is
fast. It takes little effort to test to see if elements
are consecutive. Use diff to do the test.

John

Re: Randomization_same number

Fri, 06 Nov 2009 23:48:01 -0500

> So? Then be efficient in your code. Randperm is
> fast. It takes little effort to test to see if elements
> are consecutive. Use diff to do the test.
>
> John

Thanks John. I do use the randperm function, but of course i have same trials in a row. I can find where (using diff as well), but still cannot solve the problem.

I created a mask to get rid of all the numbers i've used, but i am not sure if it is efficient and worth trying -i am new in matlab. And besides, it doesn't work properly.

Thanks

Re: Randomization_same number

John D'Errico — Sat, 07 Nov 2009 01:30:07 -0500

"D " <eclipse_dsotm@hotmail.com> wrote in message <hd2cjh$evv$1@fred.mathworks.com>...
> > So? Then be efficient in your code. Randperm is
> > fast. It takes little effort to test to see if elements
> > are consecutive. Use diff to do the test.
> >
> > John
>
> Thanks John. I do use the randperm function, but of course i have same trials in a row. I can find where (using diff as well), but still cannot solve the problem.
>
> I created a mask to get rid of all the numbers i've used, but i am not sure if it is efficient and worth trying -i am new in matlab. And besides, it doesn't work properly.
>
> Thanks

So use randperm. Then set up a loop. Scan through
the sequence. If the ith element is equal to the previous
element, then swap it with the next element in the
sequence which is not equal to it. Continue this
operation until done. If you get to the end without
success, then wrap around to the beginning.

This will be fast.

John