fread arg priority between select and colClasses
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Assessment
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Newbie friendliness
- 45/100
Research direction
Start at the fread entry point and reproduce the issue with the minimal select=1:2 and unnamed colClasses example from the report. Compare it with the named colClasses example; done means the selected columns accept the supplied types without requiring names, while existing behavior remains covered by tests.
Written by the indexing model from the issue text.
Description
require(data.table) # 1.12.4
txt <- "1,2,3\n"
fread(txt, select=1:2, colClasses=c("integer", "character"))
# Error in fread(txt, select = 1:2, colClasses = c("integer", "character")) :
# colClasses= is an unnamed vector of types, length 2, but there are 3 columns in the input. To
# specify types for a subset of columns, you can use a named vector, list format, or specify types
# using select= instead of colClasses=. Please see examples in ?fread.```
Here, the fact that select is the first 2 columns should make it clear that colClasses is sufficient for the first 2 columns, isn't it?
fread(txt, select=1:2, colClasses=c(V1="integer", V2="character"))
# V1 V2
# 1: 1 2
works but shouldn't be necessary in my opinion.
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