Broadcasting

New to Julia
,
1

I’m trying to understand broadcasting better. Here is a simple task I was working on recently:

function basis(n,x)
    return cos(n * pi * x)
end 

x = rand(10)

samples = [basis.(n,x) for n=1:5]

1- I was hoping to produce a 10 x 5 matrix, but it was an array of arrays???

2- Can I build the whole matrix with broadcasting?

2

The reason you got an Array{Array} is because basis.(n,x) creates an Array, and you put it inside an array comprehension. What you want is

x = rand(10)
 n=(1:5)'
basis.(n,x)
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3

Whoa!! Cool. So is


n = (1:5)'

just a row vector? The prime just transposes the vector?

4

Technically it’s a adjoint (transpose + complex conjugate), but for real numbers, that’s just a transpose.

Other than that technicality, you are correct.

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5

Very cool. I’m guessing that the parentheses are only needed because of the adjoint. Can you always treat a UnitRange object as a column vector?

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6 
julia> UnitRange <: AbstractVector
true

yes

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7

One small technicality is that (1:5)' is an AbstractMatirx. urrently there is no concept of row vector in Julia. Vectors are always columnar. If you transpose them you get a matrix with one row.

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