How to line break a very long 1-row string array?

General Usage
1

I have a unit row like the below. You see “” because some of the units are none. For example, there is no unit for Year.
row2 = ["" "" "" "umol/kg" "" "" "kg/m3" "decimal degrees"];
In reality it is much longer, so I would need to break them into different lines.

Why does the below give me an error? It seems that instead of considering it as a 1-row array, Julia is trying to do a vcat for the elements in these two lines?

row2 = ["" "" "" "umol/kg" "" "" 
    "kg/m3" "decimal degrees"];

Error message:

ArgumentError: number of columns of each array must match (got (6, 2))

Stacktrace:
 [1] _typed_vcat(#unused#::Type{String}, A::Tuple{Matrix{String}, Matrix{String}})
   @ Base ./abstractarray.jl:1553
 [2] typed_vcat(::Type{String}, ::Matrix{String}, ::Matrix{String})
   @ Base ./abstractarray.jl:1567
 [3] typed_hvcat(::Type{String}, ::Tuple{Int64, Int64}, ::String, ::Vararg{String, N} where N)
   @ Base ./abstractarray.jl:1957
 [4] hvcat(::Tuple{Int64, Int64}, ::String, ::Vararg{String, N} where N)
   @ Base ./abstractarray.jl:1932
 [5] top-level scope
   @ In[330]:1
 [6] eval
   @ ./boot.jl:360 [inlined]
 [7] include_string(mapexpr::typeof(REPL.softscope), mod::Module, code::String, filename::String)
   @ Base ./loading.jl:1116
2 
julia> [1 2 3
        4 5 6]
2×3 Matrix{Int64}:
 1  2  3
 4  5  6

julia> row2 = ["", "", "", "umol/kg", "", "", 
           "kg/m3", "decimal degrees"]
8-element Vector{String}:
 ""
 ""
 ""
 "umol/kg"
 ""
 ""
 "kg/m3"
 "decimal degrees"

read: Multi-dimensional Arrays · The Julia Language

1 Like
3

Thank you for the reply!

I’m able to combine this with the below code to make it work:
row2 = reshape(row2, (1,8));

4

you can also hack it as

julia> row2 = ["" "" "" "umol/kg" "" "\
           " "kg/m3" "decimal degrees"]
1×8 Matrix{String}:
 ""  ""  ""  "umol/kg"  ""  ""  "kg/m3"  "decimal degrees"

by leaving a " un-closed, parser will continue to next line, the \ cancels the line-breaking \n that was suppose to be there.

1 Like
5

In Julia 1.7 there will also be the option

julia> row2 = ["" "" "" "umol/kg" "" "";;
               "kg/m3" "decimal degrees"]
1×8 Matrix{String}:
 ""  ""  ""  "umol/kg"  ""  ""  "kg/m3"  "decimal degrees"

but I would recommend letting go of Matlab habits and just use a 1D vector.

4 Likes
6

Many thanks! How do I use a 1D vector in this case?

7

You construct it as shown earlier,

julia> vec2 = ["", "", "", "umol/kg", "", "", 
               "kg/m3", "decimal degrees"]
8-element Vector{String}:
 ""
 ""
 ""
 "umol/kg"
 ""
 ""
 "kg/m3"
 "decimal degrees"

Using it is up to the rest of your code. It depends on what you do more exactly with it, but usually a 1D vector of strings should be at least as easy to work with as a 1×N matrix in Julia.

1 Like
8

You can (equivalently) just use permutedims(row2)

Another alternative is to use a multi-line comment to absorb the line break:

row2 = ["" "" "" "umol/kg" "" "" #=
=#    "kg/m3" "decimal degrees"]

#= ... =# can generally be used for line continuation in Julia.

3 Likes
9

It’s great to learn this below trick! Many thanks for sharing!

#= ... =# can generally be used for line continuation in Julia.

10

This is useful, but I still wouldn’t mind a line continuation syntax which doesn’t need something on both lines. Not a big deal though.

1 Like
11

I agree. Julia is designed to not use line breakers, but from time to time, my program would throw out an error because of breaking a line of code into multiple lines. They can usually be fixed by simply putting everything into one long line.