Give fcase an "as factor" option

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#5,327 8 comments 1 reaction 0 assignees View on GitHub

A pull request for this has already been merged.

  • #4843 by @jangorecki — merged

Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
25/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
r
Domain
data

Research direction

Start by reviewing merged pull request #4843, which is linked from this issue, and compare it with the requested fcase factor option. Check whether the implementation supports factor levels in fcase order; the work is done when the requested behavior is covered and the issue's example is satisfied.

Written by the indexing model from the issue text.

Description

feature request

I looked for this as an open issue and did not see it. I use fcase to create categorical variables. These are almost always character. However, most of the time, I need them as factors, which requires me to retype the same factor levels, often in the same order I used them in fcase. My request is to add an option to have fcase create the factor variable directly, using the order from fcase itself. See below for a rough example.

If you wanted to be fancy, you could allow for other options too, like factor = "reverse" (to set the factor order level in the opposite sequence from the fcase statement) or even allow for a custom order by using numbers (e.g., factor = c(2, 4, 1, 3)). But just the basic version would be very helpful.

dt[, 
      newvar :=
          fcase(
              logic1 = "category 1",
              logic2 = "category 2",
              logic3 = "category 3",
              default = "category 4"
              )]
dt[, newvar := factor(newvar, levels = c("category 1", "category 2", "category 3", "category 4")]

would become

dt[, 
      newvar :=
          fcase(
              logic1 = "category 1",
              logic2 = "category 2",
              logic3 = "category 3",
              default = "category 4",
              factor = TRUE
              )]

I know you all have tons of more important things on your plate. Regardless of whether this can be done, thanks for all your help in keeping data.table going forward.

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