I'm trying to draw n -- say, 10 for simplicity -- samples from an array in Julia. Using the function wsample, ndraws below gives me what I wanted
using Distributions
population = [ 1, 10 ]
weights = [ .4, .6 ]
population_idx = wsample( population, weights, 10 ) # i.e. population indices
ndraws = population[ population_idx ]
I'm using Julia 0.2. Is there a way to do the same thing without the indices? In R for instance, we have
ndraws <- sample( population, size = 10, replace = TRUE, prob = weights )
The docs here suggests there is i.e. doing this
ndraws = wsample( population, weights, 10 )
should give me, err, exactly what I want? Note too, that in the docs, the argument name for number of draws is n but looking in the source code of sample.jl, it refers to k.
wsample(population, weights, n) returns n samples from population (not the indexes). This is in the Distributions package.
For example,
julia> using Distributions
julia> wsample(["a", "b"], [0.3, 0.7], 10)
10-element Array{ASCIIString,1}:
"a"
"b"
"b"
"b"
"b"
"b"
"b"
"b"
"a"
"b"
If what you want is to draw indexes, you can use 1:k as the population, for example, wsample(1:k, weights, n).