MATLAB: Hi – please what is the difference between normrnd and randn

normrndrandn

How to use normrnd to generate random numbers from normal distribution with specific mean and variance ?

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1. what is the difference between normrnd and randn?

doc normrnd
 r = normrnd(mu,sigma) generates a random number from the normal distribution with mean
 parameter mu and standard deviation parameter sigma.
doc randn
 X = randn returns a random scalar drawn from the standard normal distribution.

"Standard normal distribution" is a mean of 0.0 and a standard deviation of 1.0 . This means:

normrnd(mu, sigma) = randn * sigma + mu

2. How to use normrnd to generate random numbers from normal distribution with specific mean and variance ?

Simply by calling: normrnd(mu, sigma)

Remember that normrnd uses the standard deviation, which is the square root of the variance.

Do you know the doc and help commands? You find the documentation of the current Matlab version online also: https://www.mathworks.com/help/index.html

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MATLAB: What is the difference between mvnrnd and normrnd

mvnrnd() is the function used to generate pseudo random numbers that follow multi variate normal distribution. mvnrnd() is more for creating correlated random variables normrnd() is the function used to generate pseudo random numbers that follow normal distribution. normrnd() is generally faster than mvnrnd(). For more information on mvnrnd() and normrnd() follow the documentation http://www.mathworks.com/help/stats/mvnrnd.html

http://www.mathworks.com/help/stats/normrnd.html

MATLAB: Multiple runs of normrnd vs. one run of normrnd with several outputs

Yes. But why not test it yourself?

rng(17)
normrnd(0,1)
ans =
     -0.39509
normrnd(0,1)
ans =
      0.14056
normrnd(0,1)
ans =
      -1.5172

As you can see, these are the first three elements of the next call.

rng(17)
normrnd(0,1,[10,1])
ans =
     -0.39509
      0.14056
      -1.5172
       -1.882
      0.79651
      0.24127
      0.28683
      0.26861
      -2.1682
     -0.15616
normrnd(0,1,[10,1])
ans =
       1.7974
      -1.4667
       0.3709
      0.78102
      -1.3599
      0.34756
     0.084283
      0.23211
    -0.043727
     -0.09342
rng(17)
normrnd(0,1,[10,2])
ans =
     -0.39509       1.7974
      0.14056      -1.4667
      -1.5172       0.3709
       -1.882      0.78102
      0.79651      -1.3599
      0.24127      0.34756
      0.28683     0.084283
      0.26861      0.23211
      -2.1682    -0.043727
     -0.15616     -0.09342

Note that I created them as column vectors so you can see the stream of numbers is indeed the same. Had I created the array as 2x10, the numbers would have been the same, but they would have been stuffed in the array in a different sequence. But this is just a question of how MATLAB stores the elements in an array.

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Related Solutions

MATLAB: What is the difference between mvnrnd and normrnd

MATLAB: Multiple runs of normrnd vs. one run of normrnd with several outputs

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