Random number generator

Question

5.00/5 (1 vote)

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C#

MatLab

Does anyone have a random number generator in c# similar to the functions "randn" and rand in matlab

Posted 5-Aug-11 7:23am

Ravi-original

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Comments

Dr.Walt Fair, PE 5-Aug-11 13:38pm

Is there a problem with using the normal one in C#?

Ravi-original 5-Aug-11 14:47pm

The normal C# random number generator does not generate according to any distribution such as normal distribution as done by "randn" function in matlab. I want a random number generator which generates according a distribution which we assign to the random number

Sir.Ixildore 5-Aug-11 15:11pm

I was looking at randn and it seems it produces an array of random number depending on how you define the scope of the result(max, min, size of the array, and seed). Then it shouldn't be a random number generator you are looking for, instead, an array of random numbers generator.

6 solutions

Solution 1

Try as below.

C#

Random random = new Random();
int randomNumber = random.Next(0, 100);

Posted 5-Aug-11 7:24am

RaisKazi

Comments

Espen Harlinn 5-Aug-11 13:42pm

My 5

RaisKazi 5-Aug-11 13:42pm

Thanks Espen.

Alexandru Ghiondea 5-Aug-11 14:00pm

The way the current solution is wrote, the same numbers will be generated every-time you run your app.

You should provide a seed to the Random number generator. I usually use (int)DateTime.Now.Ticks.

Thanks,
Alex

Wjousts 5-Aug-11 14:30pm

No it won't. Read the docs:

Initializes a new instance of the Random class, using a time-dependent default seed value.

The parameterless constructor basically does what you suggest internally.

Alexandru Ghiondea 5-Aug-11 14:31pm

You are correct! I was not aware of this - thanks! :)

Alex

RaisKazi 5-Aug-11 14:35pm

Glad to see multiple ideas around this topic. Really, discussion evolves the perfection in solution.
Cheers Guys.

RaisKazi 5-Aug-11 14:18pm

Yes you are right Alexandru. I have just shown how to get Random Number in C#. Questioner then can use it as per their logic.

Solution 2

Random.Next generates a random number whose value ranges from zero to less than Int32.MaxValue
Reference Link :- Random.Next Method[^]
have a look at CP-[Simple Random Number Generation][^] article which enable you to learn some basics of Random number generation.

Posted 5-Aug-11 7:54am

RaviRanjanKr

Solution 3

If your concern is that the Random class is time dependent/seed dependent and calling .Next() multiple times may have resulted in the same value then you must have created your object in the method scope. Try having a reference of the Random object in the class scope or if you really want to have that object locally you can delay the call to the next .Next() call by putting delays/sleep etc. You should have a pretty decent random number results. You can refer to this [MSDN link]

Posted 5-Aug-11 8:17am

Sir.Ixildore

Updated 5-Aug-11 8:18am

Solution 6

You may also equate the cumulative of the random number extracted with the Random.Next to the cumulative of the normal distribution and then compute corresponding normal random number (yes you have to do some numeric computations).

Posted 3-Jan-12 5:51am

CPallini

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YvesDaoust · Accepted Answer · 2011-08-05T09:13:00

Solution 4

A simple way go get a normally distributed random number:

- accumulate N uniformly distributed numbers, say in range 0..R.

- substract the mean, NR/2.

- divide by the standard deviation, Sqrt(NR^2/12).

The larger N, the better the approximation. Use N=10.

Also see http://en.wikipedia.org/wiki/Box-Muller_transformation[^].

Posted 5-Aug-11 9:13am

YvesDaoust

Updated 5-Aug-11 9:18am

v4

Comments

Sergey Alexandrovich Kryukov 6-Aug-11 3:35am

My 5. It's wonderful: only you paid attention for the requirement of normal distribution; but all the votes got the first answer completely ignoring the requirement.
--SA

YvesDaoust 6-Aug-11 5:19am

Well, in this question one letter was important: the 'n' at the end of 'rand'. I wouldn't be surprised most of them missed it.

Thanks for the comment.

- Yves

Ravi-original 3-Jan-12 11:15am

You are absolutely correct. Everyone missed it. Thanks

Ravi-original 3-Jan-12 11:16am

Your method might just work but I found and validated a library that worked really well

Ravi-original · Accepted Answer · 2012-01-03T05:13:00

Solution 5

I found a library by metanumeric which generates random numbers based on the distribution we set e.g. normal, exponential etc.

This is the link for the library.
http://metanumerics.codeplex.com/[^]

worked really well for me.

Posted 3-Jan-12 5:13am

Ravi-original