rand documentation says it draws iid uniformly distributed values in the half-open unit interval [0,1) which includes zero but… Is rand ever throwing a zero? I have tried several times with minimum(rand(1_000_000_000)) and it is always strictly greater than zero.

[image] aerdely: it draws iid uniformly distributed values in the half-open unit interval [0,1) which includes zero Being that the case, that is what surprises me: why including zero? And so, why not including 1?

See this discussion if you want the 1 instead: [image] Random number in (0,1] General Usage I want a random Float64 in the interval (0,1]. I understand rand() returns a number in [0,1). Should I just use 1-rand() ? As for the reason: various conventions exist, this…

If my math is correct, and I didn’t introduce float point imprecision, I think the probability of drawing at least one zero even in 100 million draws is fairly small. N = 1_000_000_000 #Number of random draws logp = log(1-eps()) #Log probability not drawing zero on a given trial t = logp*N #Log p…

Well, this seems like a disadvantage for probabilistic simulation since it needs iid uniform values on the open unit interval (0,1), that is excluding both 0 and 1. What would be the fastest way to eliminate the possibility of a zero with rand?

[image] aerdely: What would be the fastest way to eliminate the possibility of a zero with rand? Don’t know about fastest, but this is a quick workaround: function rand_interior(rng, T) while true z = rand(rng, T) iszero(z) || return z end end [image] aerdely: a …

I can assure you that zero is possible for a decimal floating point system (as oppose to a binary floating point system) function PDFP_randomPDFPbetweenZeroandOne() DEFAULT_PRECISION[] > 0 ? newmantissa = rand(0:9,DEFAULT_PRECISION[]) : newmantissa = [] # if the first digit is …

Sampling from the range [0,1) is pretty standard. What languages do something else?

This is true but these powerball tickets are very cheap. If you’re writing robust code you do need to account for the possibility of getting zero.

if you prefer no zeros and no ones (and, for simplicity, only want Float64s) function openrand() result = rand() while iszero(result) result = rand() end return result end

Is it really possible for rand to throw a zero?

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robsmith11 September 7, 2019, 5:09pm 10

Keep in mind that if you’re using Float64s, then the probability of rand() producing an exact zero is likely far less than other important bits getting flilpped in non-ECC memory…

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Is it really possible for rand to throw a zero?

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