jimjam-slam commented on issue #45901:
URL: https://github.com/apache/arrow/issues/45901#issuecomment-2785340576
@amoeba Apologies for the slow reply! For R users, `{readr}` supports ragged
CSVs — it throws a warning for the short rows but still fills them with a
type-specific `NA`:
```r
csv_string <- "name,group,score
North,A,5
East,A
West,B,7
South
"
df <- readr::read_csv(csv_string)
#
# Rows: 4 Columns: 3
# ── Column specification
──────────────────────────────────────────────────────────────
# Delimiter: ","
# chr (2): name, group
# dbl (1): score
#
# ℹ Use `spec()` to retrieve the full column specification for this data.
# ℹ Specify the column types or set `show_col_types = FALSE` to quiet this
message.
# Warning message:
# One or more parsing issues, call `problems()` on your data frame for
details, e.g.:
# dat <- vroom(...)
# problems(dat)
df
# # A tibble: 4 × 3
# name group score
# <chr> <chr> <dbl>
# 1 North A 5
# 2 East A NA
# 3 West B 7
# 4 South NA NA
readr::problems(df)
# # A tibble: 2 × 5
# row col expected actual file
# <int> <int> <chr> <chr> <chr>
# 1 3 2 3 columns 2 columns
/private/var/folders/v3/ktxzq5ks2cz4xbvn975sp…
# 2 5 1 3 columns 1 columns
/private/var/folders/v3/ktxzq5ks2cz4xbvn975sp…
```
The `{readr}` package also has `melt_csv()` that is specifically designed
for ragged data (the function has been superseded and moved into the `{meltr}`
package but currently still remains in `{readr}`):
```r
df2 <- readr::melt_csv(csv_string)
# Warning message:
# `melt_csv()` was deprecated in readr 2.0.0.
# ℹ Please use `meltr::melt_csv()` instead
# This warning is displayed once every 8 hours.
# Call `lifecycle::last_lifecycle_warnings()` to see where this warning was
generated.
df2
# # A tibble: 12 × 4
# row col data_type value
# <dbl> <dbl> <chr> <chr>
# 1 1 1 character name
# 2 1 2 character group
# 3 1 3 character score
# 4 2 1 character North
# 5 2 2 character A
# 6 2 3 integer 5
# 7 3 1 character East
# 8 3 2 character A
# 9 4 1 character West
# 10 4 2 character B
# 11 4 3 integer 7
# 12 5 1 character South
```
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