within_group: Execute code within a group
In multiplyr: Data Manipulation with Parallelism and Shared Memory Matrices

Description Usage Arguments Value See Also Examples

This is the mainstay of parallel computation for a data frame. This will execute the specified expression within each group. Each group will have a persistent environment, so that variables created in that environment can be referred to by, for example, later calls to summarise. This environment contains active bindings to the columns of that data frame.

1	within_group(.self, expr)

`.self`	Data frame
`expr`	Code to execute

Data frame

Other data manipulations: mutate, nsa, reduce, summarise, transmute, within_node

dat <- Multiplyr (G = rep(c("A", "B"), each=50),
                  m = rep(c(5, 10), each=50),
                  alloc=1)
dat %>% group_by (G) %>% mutate (x=rnorm(length(m), mean=m))
dat %>% within_group ({
    mdl <- lm (x ~ 1)
})
dat %>% summarise (x.mean = coef(mdl)[[1]])
dat %>% shutdown()