melt_delim_chunked | R Documentation |
For certain non-rectangular data formats, it can be useful to parse the data into a melted format where each row represents a single token.
melt_delim_chunked( file, callback, chunk_size = 10000, delim, quote = "\"", escape_backslash = FALSE, escape_double = TRUE, locale = default_locale(), na = c("", "NA"), quoted_na = TRUE, comment = "", trim_ws = FALSE, skip = 0, progress = show_progress(), skip_empty_rows = FALSE ) melt_csv_chunked( file, callback, chunk_size = 10000, locale = default_locale(), na = c("", "NA"), quoted_na = TRUE, quote = "\"", comment = "", trim_ws = TRUE, skip = 0, progress = show_progress(), skip_empty_rows = FALSE ) melt_csv2_chunked( file, callback, chunk_size = 10000, locale = default_locale(), na = c("", "NA"), quoted_na = TRUE, quote = "\"", comment = "", trim_ws = TRUE, skip = 0, progress = show_progress(), skip_empty_rows = FALSE ) melt_tsv_chunked( file, callback, chunk_size = 10000, locale = default_locale(), na = c("", "NA"), quoted_na = TRUE, quote = "\"", comment = "", trim_ws = TRUE, skip = 0, progress = show_progress(), skip_empty_rows = FALSE )
melt_delim_chunked()
and the specialisations melt_csv_chunked()
,
melt_csv2_chunked()
and melt_tsv_chunked()
read files by a chunk of rows
at a time, executing a given function on one chunk before reading the next.
A tibble()
of four columns:
row
, the row that the token comes from in the original file
col
, the column that the token comes from in the original file
data_type
, the data type of the token, e.g. "integer"
, "character"
,
"date"
, guessed in a similar way to the guess_parser()
function.
value
, the token itself as a character string, unchanged from its
representation in the original file.
If there are parsing problems, a warning tells you
how many, and you can retrieve the details with problems()
.
Other chunked:
callback
# Cars with 3 gears f <- function(x, pos) subset(x, data_type == "integer") melt_csv_chunked(meltr_example("mtcars.csv"), DataFrameCallback$new(f), chunk_size = 5)
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