future_by: Apply a Function to a Data Frame Split by Factors via Futures

Description

Apply a Function to a Data Frame Split by Factors via Futures

Usage

future_by(data, INDICES, FUN, ..., simplify = TRUE)

Arguments

data

An R object, normally a data frame, possibly a matrix.

INDICES

A factor or a list of factors, each of length nrow(data).

FUN

a function to be applied to (usually data-frame) subsets of data.

simplify

logical: see base::tapply.

…

Additional arguments pass to future_lapply() and then to FUN().

Value

An object of class "by", giving the results for each subset. This is always a list if simplify is false, otherwise a list or array (see base::tapply). See also base::by() for details.

Details

Internally, data is grouped by INDICES into a list of data subset elements which is then processed by future_lapply(). When the groups differ significantly in size, the processing time may differ significantly between the groups. To correct for processing-time imbalances, adjust the amount of chunking via arguments future.scheduling and future.chunk.size.

Examples

Run this code

# NOT RUN {
## ---------------------------------------------------------
## by()
## ---------------------------------------------------------
library(datasets) ## warpbreaks
library(stats)    ## lm()

y0 <- by(warpbreaks, warpbreaks[,"tension"],
         function(x) lm(breaks ~ wool, data = x))

plan(multiprocess)
y1 <- future_by(warpbreaks, warpbreaks[,"tension"],
                function(x) lm(breaks ~ wool, data = x))

plan(sequential)
y2 <- future_by(warpbreaks, warpbreaks[,"tension"],
                function(x) lm(breaks ~ wool, data = x))
# }

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