# Display of arrays with row and column names

**URL:** <https://discourse.julialang.org/t/display-of-arrays-with-row-and-column-names/1961>\
**Category:** General Usage\
**Tags:** question\
**Created:** [February 7, 2017, 6:31pm UTC](https://discourse.julialang.org/t/display-of-arrays-with-row-and-column-names/1961 "2017-02-07T18:31:55Z")\
**Posts on this page:** 10\
**Page:** 1

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**Author:** ![mcreel](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mcreel/32/30088_2.png) [@mcreel](https://discourse.julialang.org/u/mcreel)\
**Post date:** [February 7, 2017, 6:31pm UTC](https://discourse.julialang.org/t/display-of-arrays-with-row-and-column-names/1961/1 "2017-02-07T18:31:55Z")

</div>

I’m aware of some previous threads discussing this topic, but I do not find any way to conveniently reproduce what I can do with Octave, e.g.,

```julia
octave:1> cnames=["this"; "that"];
octave:2> a = rand(3,2);
octave:3> prettyprint_c(a, cnames);
      this that  
     0.486 0.294
     0.166 0.328
     0.826 0.974
octave:4> rnames = ["aaa";"bbb";"ccc"];
octave:5> prettyprint(a, rnames, cnames);
             this that  
aaa 0.486 0.294
bbb 0.166 0.328
ccc 0.826 0.974
octave:6> 

```

Is something like this part of some package?

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**Author:** ![catawbasam](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/catawbasam/32/2936_2.png) [@catawbasam](https://discourse.julialang.org/u/catawbasam)\
**Post date:** [February 7, 2017, 7:09pm UTC](https://discourse.julialang.org/t/display-of-arrays-with-row-and-column-names/1961/2 "2017-02-07T19:09:58Z")

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Maybe `NamedArrays.jl`? Depending on your task, `DataFrames.jl` might also be interesting.

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**Author:** ![nalimilan](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/nalimilan/32/147_2.png) [@nalimilan](https://discourse.julialang.org/u/nalimilan)\
**Post date:** [February 7, 2017, 8:54pm UTC](https://discourse.julialang.org/t/display-of-arrays-with-row-and-column-names/1961/3 "2017-02-07T20:54:49Z")

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Definitely NamedArrays or AxisArrays. DataFrames are more intended for data base like structures (and they do not support row names).

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**Author:** ![johnmyleswhite](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/johnmyleswhite/32/31_2.png) [@johnmyleswhite](https://discourse.julialang.org/u/johnmyleswhite)\
**Post date:** [February 7, 2017, 9:01pm UTC](https://discourse.julialang.org/t/display-of-arrays-with-row-and-column-names/1961/4 "2017-02-07T21:01:14Z")

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It seems to me like there’s potentially two distinct issues here: maintaining a data structure with names and wanting to print out an existing matrix/table data structure with names. I’ve often thought we would benefit from writing a package that provides an API for printing matrices and tables with ad hoc formatting – which would include printing names.

I’ve seen people using DataFrames just because they prefer the way DataFrames are printed to the way matrices are printed.

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**Author:** ![mcreel](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mcreel/32/30088_2.png) [@mcreel](https://discourse.julialang.org/u/mcreel)\
**Post date:** [February 8, 2017, 1:39pm UTC](https://discourse.julialang.org/t/display-of-arrays-with-row-and-column-names/1961/5 "2017-02-08T13:39:07Z")

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Thanks for the suggestions. I hacked together a quick solution, which is just a proof of concept. It still takes me time to think of using loops, as I’m so used to avoiding them.

Contents of test.jl:

```julia
function prettyprint_c(a, cnames)
    for i = 1:size(a,2)
        @printf("%s ", lpad(cnames[i],8," "))
    end
    @printf("\n")
    for i = 1:size(a,1)
        for j = 1:size(a,2)
            @printf("%f ", a[i,j])
        end
        @printf("\n")
    end    
end

```

```julia
julia> include("test.jl")
prettyprint_c (generic function with 1 method)

julia> prettyprint_c(rand(2,2), cnames)
     red green  
0.538184 0.921006  
0.771004 0.036080  

julia>

```

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<div class="post-metadata">

**Author:** ![mcreel](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mcreel/32/30088_2.png) [@mcreel](https://discourse.julialang.org/u/mcreel)\
**Post date:** [February 8, 2017, 4:49pm UTC](https://discourse.julialang.org/t/display-of-arrays-with-row-and-column-names/1961/6 "2017-02-08T16:49:35Z")

</div>

Here’s another version, a little more elaborate. I haven’t figured out how to allow for user specified printing format of the numbers.

```julia
function prettyprint(a, cnames, rnames="",digits=8, decimals=4)
    # TBD: try to use this to allow using specified digits and decimals
    #fmt = @sprintf("%d",digits)"."@sprintf("%d",decimals)"%f"
    #@eval dofmt(x) = @sprintf($fmt, x)
    
    # print column names
    for i = 1:size(a,2)
        pad = digits
        if rnames != "" && i==1
            pad = 2*digits
        end    
        @printf("%s", lpad(cnames[i],pad," "))
    end
    @printf("\n")
    # print the rows
    for i = 1:size(a,1)
        if rnames != ""
            @printf("%s", lpad(rnames[i],digits," "))
        end
        for j = 1:size(a,2)
            # TBD: use fmt defined above to print array contents
            @printf("%8.4f",(a[i,j]))
        end
        @printf("\n")
    end    
end  

```

This is what it gives you:

```julia
julia> prettyprint(rand(3,2), ["r","b"], ["1","2","3"])
               r b
       1 0.1127 0.0660
       2 0.4678 0.1982
       3 0.3126 0.1833

julia> prettyprint(rand(3,2), ["r","b"])
       r b
  0.9553 0.9253
  0.8519 0.8340
  0.1447 0.1828

julia>

```

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<div class="post-metadata">

**Author:** ![stevengj](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stevengj/32/71_2.png) [@stevengj](https://discourse.julialang.org/u/stevengj)\
**Post date:** [February 8, 2017, 7:07pm UTC](https://discourse.julialang.org/t/display-of-arrays-with-row-and-column-names/1961/7 "2017-02-08T19:07:48Z")

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You could just put strings at the top of the array:

```julia
julia> cnames = ["this" "that"];

julia> a = rand(3,2);

julia> [cnames; a]
4×2 Array{Any,2}:
  "this" "that" 
 0.919038 0.959908
 0.54821 0.954816
 0.448264 0.135813

```

This prints out the strings in quotation marks, which is a little annoying, but you can eliminate the quotes in display by wrapping them in a `Text` object:

```julia
julia> [Text.(cnames); a]
4×2 Array{Any,2}:
  this that   
 0.919038 0.959908
 0.54821 0.954816
 0.448264 0.135813

```

If you want to avoid the header, you have to call the internal `showarray` function:

```julia
julia> Base.showarray(STDOUT, [Text.(cnames); a], false, header=false)
  this that   
 0.919038 0.959908
 0.54821 0.954816
 0.448264 0.135813

```

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<div class="post-metadata">

**Author:** ![mkborregaard](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mkborregaard/32/556_2.png) [@mkborregaard](https://discourse.julialang.org/u/mkborregaard)\
**Post date:** [February 8, 2017, 7:11pm UTC](https://discourse.julialang.org/t/display-of-arrays-with-row-and-column-names/1961/8 "2017-02-08T19:11:24Z")

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The `show` method in NamedArrays is very good IMHO  
[https://github.com/davidavdav/NamedArrays.jl/blob/b6a3b1d03214ba8b977b85944ea1bb47c7796495/src/show.jl#L96](https://github.com/davidavdav/NamedArrays.jl/blob/b6a3b1d03214ba8b977b85944ea1bb47c7796495/src/show.jl#L96)

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<div class="post-metadata">

**Author:** ![charleskawczynski](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/charleskawczynski/32/13783_2.png) [@charleskawczynski](https://discourse.julialang.org/u/charleskawczynski)\
**Post date:** [April 7, 2019, 6:32pm UTC](https://discourse.julialang.org/t/display-of-arrays-with-row-and-column-names/1961/9 "2019-04-07T18:32:11Z")

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This seems like a nice solution. On top of this, I’m using `Base.print_matrix`, which is giving me the format I’d like:

```julia
julia> cnames = ["this" "that"]
1×2 Array{String,2}:
 "this" "that"

julia> a = rand(3,2)
3×2 Array{Float64,2}:
 0.527699 0.416864
 0.154895 0.953161
 0.642032 0.309332

julia> Base.print_matrix(stdout, [Text.(cnames); a])
  this that
 0.5276986161946835 0.41686414033643016
 0.15489479331644973 0.9531611170842169
 0.6420319865177682 0.3093316412409517

```

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<div class="post-metadata">

**Author:** ![RaulDurand](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/rauldurand/32/2044_2.png) [@RaulDurand](https://discourse.julialang.org/u/RaulDurand)\
**Post date:** [April 27, 2019, 12:29am UTC](https://discourse.julialang.org/t/display-of-arrays-with-row-and-column-names/1961/10 "2019-04-27T00:29:41Z")

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I saw this requirement more than once including in SO. I think that a native prettyprint function for matrices would be very convenient.