process_blocks {LaF} | R Documentation |
Reads the specified file block by block and feeds each block to the specified function.
process_blocks(x, fun, ...) ## S4 method for signature 'laf' process_blocks(x, fun, columns = 1:ncol(x), nrows = 5000, allow_interupt = FALSE, progress = FALSE, ...)
x |
an object the supports the |
fun |
a function to apply to each block (see details). |
... |
additional parameters are passed on to |
columns |
an integer vector with the columns that should be read in. |
nrows |
the (maximum) number of rows to read in one block |
allow_interupt |
when TRUE the function |
progress |
show a progress bar. Note that this triggers a calculation
of the number of lines in the file which for CSV files can take some time.
When numeric |
The function should accept as the first argument the next block of data. When
the end of the file is reached this is an empty (zero row) data.frame
.
As the second argument the function should accept the output of the previous
call to the function. The first time the function is called the second
argument has the value NULL
.