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map

map(f, c...) -> collection

Transform collection c by applying f to each element. For multiple collection arguments, apply f elementwise.

julia> map((x) -> x * 2, [1, 2, 3])
3-element Array{Int64,1}:
 2
 4
 6

julia> map(+, [1, 2, 3], [10, 20, 30])
3-element Array{Int64,1}:
 11
 22
 33

Examples

julia> array = Int[1,2,3]
       map(x -> x + 1, array)
3-element Array{Int64,1}:
 2
 3
 4

julia> array = Int[1,2,3]
       map(x -> x * 2, array)
3-element Array{Int64,1}:
 2
 4
 6

julia> map((x) -> x^3, [1 2 3])
1x3 Array{Int64,2}:
 1      8       27
julia> function Foo(x,y)
                return 2(x+y)
            end
julia> map(Foo, [1 2 3], ones(1, 3))
1x3 Array{Float64,2}:
 4.0    6.0     8.0

1. Apply a function to each element of an array:

   julia> arr = [1, 2, 3, 4, 5];
   julia> map((x) -> x * 2, arr)
   5-element Array{Int64,1}:
   2
   4
   6
   8
   10

   This example applies the anonymous function (x) -> x * 2 to each element of the array arr and returns a new array with the transformed values.

2. Apply a function elementwise to multiple collections:

   julia> a = [1, 2, 3];
   julia> b = [10, 20, 30];
   julia> map(+, a, b)
   3-element Array{Int64,1}:
   11
   22
   33

   The + function is applied elementwise to the corresponding elements of arrays a and b, resulting in a new array with the sum of each pair of elements.

3. Transform strings using a custom function:

   julia> words = ["apple", "banana", "orange"];
   julia> map((s) -> uppercase(s), words)
   3-element Array{String,1}:
   "APPLE"
   "BANANA"
   "ORANGE"

   The anonymous function (s) -> uppercase(s) is applied to each string in the words array, transforming them to uppercase.

Common mistake example:

julia> arr = [1, 2, 3];
julia> map((x) -> x * 2, arr, [4, 5, 6])
ERROR: MethodError: no method matching iterate(::Int64)

In this example, the number of elements in the input arrays (arr and [4, 5, 6]) is not the same. When using map with multiple collections, ensure that all collections have the same length to avoid such errors.

See Also

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