When indexing an Array{Float64,2} julia> A = ones(1,5) 1×5 Array{Float64,2}: 1.0 1.0 1.0 1.0 1.0 julia> A[1,2:5] 4-element Array{Float64,1}: 1.0 1.0 1.0 1.0 Why am I being given an Array{Float64,1}? I’m expecting to get: 1×4 Array{Float64,2}: 1.0 1.0 1.0 1.0

A slice of a matrix is a vector, so has size (n,). If you want a 1xn matrix back, you can use A[[1], 2:5], or if you just want it to be a row vector, you can do A[1, 2:5]'

Depending on your preference, you can also use range indexing. A[1:1, 2: 5] I prefer this, because it’s consistent to that 2:5 syntax.

Thanks for replying so quickly! Seems so obvious now I know, thank you

Simple rule: the dimensionality of the output is the summed dimensionality of the indexes. So A[i,j], where i and j are Ints, gives you a scalar (zero-dimensional). You supplied one scalar and one vector, so you got a 1-dimensional output. The fun doesn’t stop there. Here’s an example that some oth…

Array{Float64,2} -> Array{Float64,1}

General Usage

Henrique_Becker September 2, 2020, 11:09pm 3

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Array{Float64,2} -> Array{Float64,1}

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