readr (version 1.0.0)

callback: Callback classes

Description

These classes are used to define callback behaviors.

Details

See Also

Other chunked: read_delim_chunked, read_lines_chunked

Examples

## If given a regular function it is converted to a SideEffectChunkCallback

# view structure of each chunk
read_lines_chunked(readr_example("mtcars.csv"), str, chunk_size = 5)

# Print starting line of each chunk
f <- function(x, pos) print(pos)
read_lines_chunked(readr_example("mtcars.csv"), SideEffectChunkCallback$new(f), chunk_size = 5)

## If combined results are desired you can use the DataFrameCallback

# Cars with 3 gears
f <- function(x, pos) subset(x, gear == 3)
read_csv_chunked(readr_example("mtcars.csv"), DataFrameCallback$new(f), chunk_size = 5)