Obtain one chunk by chunk id

get_chunk(...)

# S3 method for disk.frame
get_chunk(df, n, keep = NULL, full.names = FALSE, ...)

Arguments

...

passed to fst::read_fst or whichever read function is used in the backend

df

a disk.frame

n

the chunk id. If numeric then matches by number, if character then returns the chunk with the same name as n

keep

the columns to keep

full.names

whether n is the full path to the chunks or just a relative path file name. Ignored if n is numeric

Examples

cars.df = as.disk.frame(cars, nchunks = 2) get_chunk(cars.df, 1)
#> speed dist #> 1: 4 2 #> 2: 4 10 #> 3: 7 4 #> 4: 7 22 #> 5: 8 16 #> 6: 9 10 #> 7: 10 18 #> 8: 10 26 #> 9: 10 34 #> 10: 11 17 #> 11: 11 28 #> 12: 12 14 #> 13: 12 20 #> 14: 12 24 #> 15: 12 28 #> 16: 13 26 #> 17: 13 34 #> 18: 13 34 #> 19: 13 46 #> 20: 14 26 #> 21: 14 36 #> 22: 14 60 #> 23: 14 80 #> 24: 15 20 #> 25: 15 26 #> speed dist
get_chunk(cars.df, 2)
#> speed dist #> 1: 15 54 #> 2: 16 32 #> 3: 16 40 #> 4: 17 32 #> 5: 17 40 #> 6: 17 50 #> 7: 18 42 #> 8: 18 56 #> 9: 18 76 #> 10: 18 84 #> 11: 19 36 #> 12: 19 46 #> 13: 19 68 #> 14: 20 32 #> 15: 20 48 #> 16: 20 52 #> 17: 20 56 #> 18: 20 64 #> 19: 22 66 #> 20: 23 54 #> 21: 24 70 #> 22: 24 92 #> 23: 24 93 #> 24: 24 120 #> 25: 25 85 #> speed dist
get_chunk(cars.df, 1, keep = "speed")
#> speed #> 1: 4 #> 2: 4 #> 3: 7 #> 4: 7 #> 5: 8 #> 6: 9 #> 7: 10 #> 8: 10 #> 9: 10 #> 10: 11 #> 11: 11 #> 12: 12 #> 13: 12 #> 14: 12 #> 15: 12 #> 16: 13 #> 17: 13 #> 18: 13 #> 19: 13 #> 20: 14 #> 21: 14 #> 22: 14 #> 23: 14 #> 24: 15 #> 25: 15 #> speed
# if full.names = TRUE then the full path to the chunk need to be provided get_chunk(cars.df, file.path(attr(cars.df, "path"), "1.fst"), full.names = TRUE)
#> speed dist #> 1: 4 2 #> 2: 4 10 #> 3: 7 4 #> 4: 7 22 #> 5: 8 16 #> 6: 9 10 #> 7: 10 18 #> 8: 10 26 #> 9: 10 34 #> 10: 11 17 #> 11: 11 28 #> 12: 12 14 #> 13: 12 20 #> 14: 12 24 #> 15: 12 28 #> 16: 13 26 #> 17: 13 34 #> 18: 13 34 #> 19: 13 46 #> 20: 14 26 #> 21: 14 36 #> 22: 14 60 #> 23: 14 80 #> 24: 15 20 #> 25: 15 26 #> speed dist
# clean up cars.df delete(cars.df)