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arraysjulia
fhucho
fhucho

Reputation: 34530

Find first index of an item in an array in Julia

What is the simplest way to find the first index of some item in an array in Julia?

Upvotes: 25

Views: 22074

Answers (2)

Mohammad Nazari
Mohammad Nazari

Reputation: 3025

You can use ‍‍findfirst as follows:

A = [1, 4, 2, 3, 2]

function myCondition(y)
    return 2 == y
end

println( findfirst(myCondition, A) )

# output: 3

you can read more in this Link

Upvotes: 8

tholy
tholy

Reputation: 12179

There is findfirst and more generally findnext, which allows you to restart where you left off. One advantage of these two is that you don't need to allocate an output array, so the performance will be better (if you care).

Also, keep in mind that (unlike some other languages you may be used to) Julia's loops are fast, and as a consequence you can always write such simple functions yourself. To see what I mean, take a look at the implementation of findnext (in base/array.jl); there's nothing "fancy" about it, yet you get performance that is just as good as what you'd get if you had implemented it in C.

Upvotes: 38

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