CODEWITHSUNDEEP
matlabprobabilityprobability-theoryprobability-density
Jack2007
Jack2007

Reputation: 59

a function display logarithm of a pdf in matlab

I need to calculate the density of 50 in a standard normal distribution, actually, the result will return to 0 by pdf('norm',50,0,1), then I try to display the logarithm of it,it doesn't work with log(pdf('norm',50,0,1)). In R, we can do like dnorm(50,log = TRUE), any similar function in MATLAB? I did not find it. thanks

Upvotes: 1

Views: 63

Answers (1)

Luis Mendo
Luis Mendo

Reputation: 112679

If you compute the pdf evaluated at 50, you get 0 because of finite precision (spefically, the result is less than realmin). You should compute the logarithm directly. From the definition, the logarithm of a standard normal pdf evaluated at 50 is

>> format long %// to show more decimals
>> -50^2/2 - .5*log(2*pi)
ans =
   -1.250918938533205e+003

Upvotes: 2

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