# CategoricalArrays Binning

**URL:** <https://discourse.julialang.org/t/categoricalarrays-binning/99400>\
**Category:** Data\
**Tags:** categoricalarrays\
**Created:** [May 25, 2023, 7:00pm UTC](https://discourse.julialang.org/t/categoricalarrays-binning/99400 "2023-05-25T19:00:33Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![astro-kevin](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/astro-kevin/32/43342_2.png) [@astro-kevin](https://discourse.julialang.org/u/astro-kevin)\
**Post date:** [May 25, 2023, 7:00pm UTC](https://discourse.julialang.org/t/categoricalarrays-binning/99400/1 "2023-05-25T19:00:33Z")

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When using the `cut` function of CategoricalArrays, it returns CategoricalArray objects which contain CategoricalValue objects like `[0,1)`. However, I don’t seem to understand how to access the value that was cut, for example, if I wanted the midpoint of the bin, I would run a mean over the two numbers, but since they are essentially strings, I can’t do that. Is there some way to do this that I don’t know about?

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**Author:** ![bkamins](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/bkamins/32/208538_2.png) [@bkamins](https://discourse.julialang.org/u/bkamins)\
**Post date:** [May 25, 2023, 7:09pm UTC](https://discourse.julialang.org/t/categoricalarrays-binning/99400/2 "2023-05-25T19:09:34Z")

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You cannot by default, unless you encode it using a custom formatted. Maybe for your use case you want to use histogram instead?

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<div class="post-metadata">

**Author:** ![astro-kevin](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/astro-kevin/32/43342_2.png) [@astro-kevin](https://discourse.julialang.org/u/astro-kevin)\
**Post date:** [May 25, 2023, 8:07pm UTC](https://discourse.julialang.org/t/categoricalarrays-binning/99400/3 "2023-05-25T20:07:07Z")

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I don’t know how Histogram would work, because I need to create the bins, and then get the mean and standard deviation of another variable in each of the bins.

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<div class="post-metadata">

**Author:** ![bkamins](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/bkamins/32/208538_2.png) [@bkamins](https://discourse.julialang.org/u/bkamins)\
**Post date:** [May 26, 2023, 1:37am UTC](https://discourse.julialang.org/t/categoricalarrays-binning/99400/4 "2023-05-26T01:37:11Z")

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If you do not know how to use histogram the simplest thing is to do the following (I show it to you by example):

```julia
julia> using DataFrames, CategoricalArrays, Statistics

julia> df = DataFrame(rand(10, 2), [:ref, :other])
10×2 DataFrame
 Row │ ref other
     │ Float64 Float64
─────┼─────────────────────
   1 │ 0.153328 0.464341
   2 │ 0.794552 0.687084
   3 │ 0.860548 0.66624
   4 │ 0.252829 0.199308
   5 │ 0.709457 0.981467
   6 │ 0.2814 0.355272
   7 │ 0.819591 0.413013
   8 │ 0.575109 0.169053
   9 │ 0.551803 0.0971433
  10 │ 0.540336 0.64679

julia> df.bin = cut(df.ref, 3);

julia> df
10×3 DataFrame
 Row │ ref other bin
     │ Float64 Float64 Cat…
─────┼────────────────────────────────────────────────────────
   1 │ 0.153328 0.464341 Q1: [0.15332816708897712, 0.5403…
   2 │ 0.794552 0.687084 Q3: [0.7094574019643611, 0.86054…
   3 │ 0.860548 0.66624 Q3: [0.7094574019643611, 0.86054…
   4 │ 0.252829 0.199308 Q1: [0.15332816708897712, 0.5403…
   5 │ 0.709457 0.981467 Q3: [0.7094574019643611, 0.86054…
   6 │ 0.2814 0.355272 Q1: [0.15332816708897712, 0.5403…
   7 │ 0.819591 0.413013 Q3: [0.7094574019643611, 0.86054…
   8 │ 0.575109 0.169053 Q2: [0.5403359070225858, 0.70945…
   9 │ 0.551803 0.0971433 Q2: [0.5403359070225858, 0.70945…
  10 │ 0.540336 0.64679 Q2: [0.5403359070225858, 0.70945…

julia> combine(groupby(df, :bin), :ref .=> [minimum, maximum, mean], :other .=> [mean, std])
3×6 DataFrame
 Row │ bin ref_minimum ref_maximum ref_mean other_mean other_std
     │ Cat… Float64 Float64 Float64 Float64 Float64
─────┼──────────────────────────────────────────────────────────────────────────────────────────────
   1 │ Q1: [0.15332816708897712, 0.5403… 0.153328 0.2814 0.229186 0.339641 0.133206
   2 │ Q2: [0.5403359070225858, 0.70945… 0.540336 0.575109 0.555749 0.304329 0.298752
   3 │ Q3: [0.7094574019643611, 0.86054… 0.709457 0.860548 0.796037 0.686951 0.23253

```