How a generate random numbers within a probabilistic range?

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Nikolas Spiliopoulos
评论： Nikolas Spiliopoulos 2016-11-3
Hi there,
I would like to generate random numbers for an input of 48 variables within a probabilistic range. I managed to get results for a particular range (lets say -0.02 +0.02), using rand function. However how can I do the same for a probabilistic range like this:
50% probability the range to be -0.01 +0.01, 30% probability the range to be -0.02 +0.02 and so on.
many thanks
Nikolas
  2 个评论
Torsten
Torsten 2016-11-3
How can the probability become smaller for a wider range ?
Best wishes
Torsten.
Nikolas Spiliopoulos
Nikolas Spiliopoulos 2016-11-3
Hi again,
thanks for the prompt reply.
Well it has to do with the problem, it's more likely the values to change within a range of -0.01 to +0.01 rather than a range of -0.02 +0.02.
hope that helps
Nikolas

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回答（1 个）

Adam
Adam 2016-11-3
编辑：Adam 2016-11-3
You could just do a simple 2 layer approach if rand gives you an acceptable distribution within each of your ranges.
e.g.
ranges = [-0.01 0.01; -0.02 0.02; -0.05 0.05];
rangeProbabilities = [0.5 0.3 0.2];
rangeVal = rand( )
rangeIdx = find( cumsum( rangeProbabilities ) >= rangeVal , 1 )
n = 48;
randomNumbers = ( rand( n, 1 ) -0.5 ) * 2 * ranges( rangeIdx, 2 ); % Produce n random numbers in range
Note that last line assumes your ranges are symmetric (in which case there's no point storing the 1st column anyway). If not then it is still simple enough to ensure a random number falls within a single predefined range.

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