CODEWITHSUNDEEP
for-loopdataframejulia
kintero
kintero

Reputation: 75

How to save Julia for loop returns in an array or dataframe?

I am trying to apply a function over each row of a DataFrame as the code shows.

using RDatasets
iris = dataset("datasets", "iris")

function mean_n_var(x)
    mean1=mean([x[1], x[2], x[3], x[4]])
    var1=var([x[1], x[2], x[3], x[4]])
    rst=[mean1, var1]
    return rst
end

mean_n_var([2,4,5,6])

for row in eachrow(iris[1:4])
    println(mean_n_var(convert(Array, row)))
end

However, instead of printing results, I'd like to save them in an array or another DataFrame.

Thanks in advance.

Upvotes: 4

Views: 761

Answers (1)

Bogumił Kamiński
Bogumił Kamiński

Reputation: 69899

I thought it is worth to mention some more options available over what was already mentioned.

I assume you want a Matrix or a DataFrame. There are several possible approaches.

First is the most direct to get a Matrix:

mean_n_var(a) = [mean(a), var(a)]
hcat((mean_n_var(Array(x)) for x in eachrow(iris[1:4]))...) # rows
vcat((mean_n_var(Array(x)).' for x in eachrow(iris[1:4]))...) # cols

another possible approach is vectorized, e.g.:

mat_iris = Matrix(iris[1:4])
mat = hcat(mean(mat_iris, 2), var(mat_iris, 2))
df = DataFrame([vec(f(mat_iris, 2)) for f in [mean,var]], [:mean, :var])
DataFrame(mat) # this constructor also accepts variable names on master but is not released yet

Upvotes: 3

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