# Map a scalar function over collection of arrays
**URL:** https://discourse.julialang.org/t/map-a-scalar-function-over-collection-of-arrays/4634
**Category:** General Usage
**Created:** [July 4, 2017, 9:23am UTC](https://discourse.julialang.org/t/map-a-scalar-function-over-collection-of-arrays/4634 "2017-07-04T09:23:57Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@mauro3](https://discourse.julialang.org/u/mauro3)
#### Post date: [July 4, 2017, 9:23am UTC](https://discourse.julialang.org/t/map-a-scalar-function-over-collection-of-arrays/4634/1 "2017-07-04T09:23:57Z")
In Julia `map(rad2deg, ([1],[2]) )` works. In 0.6 is is deprecated:
```julia
julia> map(rad2deg, ([1], [2]))
WARNING: rad2deg{T <: Real}(x::AbstractArray{T}) is deprecated, use rad2deg.(x) instead.
Stacktrace:
[1] depwarn(::String, ::Symbol) at ./deprecated.jl:70
[2] rad2deg(::Array{Int64,1}) at ./deprecated.jl:57
[3] map(::Base.Math.#rad2deg, ::Tuple{Array{Int64,1},Array{Int64,1}}) at ./tuple.jl:159
[4] eval(::Module, ::Any) at ./boot.jl:235
[5] eval_user_input(::Any, ::Base.REPL.REPLBackend) at ./REPL.jl:66
[6] macro expansion at ./REPL.jl:97 [inlined]
[7] (::Base.REPL.##1#2{Base.REPL.REPLBackend})() at ./event.jl:73
while loading no file, in expression starting on line 0
([57.2958], [114.592])
```
using an array comprehension works:
```julia
julia> [rad2deg.(i) for i in ([1], [2])]
2-element Array{Array{Float64,1},1}:
[57.2958]
[114.592]
```
as I can add the `.`. Is there a way to still use `map`?
---
### Author:  [@davidanthoff](https://discourse.julialang.org/u/davidanthoff)
#### Post date: [July 4, 2017, 10:42am UTC](https://discourse.julialang.org/t/map-a-scalar-function-over-collection-of-arrays/4634/2 "2017-07-04T10:42:13Z")
I guess this is an example where [https://github.com/JuliaLang/julia/issues/21875](https://github.com/JuliaLang/julia/issues/21875) would help.
---
### Author:  [@ohsonice](https://discourse.julialang.org/u/ohsonice)
#### Post date: [July 4, 2017, 4:33pm UTC](https://discourse.julialang.org/t/map-a-scalar-function-over-collection-of-arrays/4634/3 "2017-07-04T16:33:54Z")
Is using an anonymous function is the best workaround for now?
```julia
julia> x = ([1,2],[2,3]);
julia> @btime [rad2deg.(i) for i in x];
191.066 ns (4 allocations: 304 bytes)
julia> @btime map(x->rad2deg.(x), x);
90.195 ns (3 allocations: 224 bytes)
julia> @btime broadcast.(rad2deg,x);
9.492 μs (11 allocations: 480 bytes)
```
---
### Author:  [@stevengj](https://discourse.julialang.org/u/stevengj)
#### Post date: [July 4, 2017, 6:49pm UTC](https://discourse.julialang.org/t/map-a-scalar-function-over-collection-of-arrays/4634/4 "2017-07-04T18:49:01Z")
> [@ohsonice](#):
>
> Is using an anonymous function is the best workaround for now?
Your benchmarks were misleading because they used a global variable `x`. When using BenchmarkTools, you have to be careful to splice in the values of globals:
```julia
julia> @btime broadcast.(rad2deg,x);
7.395 μs (11 allocations: 480 bytes)
julia> @btime broadcast.(rad2deg,$x);
76.135 ns (5 allocations: 256 bytes)
julia> @btime map(x->rad2deg.(x), $x);
68.809 ns (3 allocations: 224 bytes)
julia> @btime [rad2deg.(i) for i in $x];
102.691 ns (4 allocations: 304 bytes)
julia> @btime map.(rad2deg, $x);
86.099 ns (5 allocations: 256 bytes)
```
So, the `broadcast.(....)` solution is just fine.