dapply: Apply a Function to Subsets of Data Frame.
In 0liver0815/onc-crmpack-test: Object-Oriented Implementation of CRM Designs

Description Usage Arguments Value Examples

dapply splits the data df into the subsets defined by f, and applies function FUN to each of the subset. All the results are row-binded and returned as data.frame object.

1	dapply(df, f, FUN, ...)

`df`	(`data frame`) data set to be divided into groups.
`f`	(`factor` or `formula` or `list`) a factor in the sense that `as.factor(f)` defines the grouping, or a `list` of such factors in which case their interaction is used for the grouping. `f` can also be a formula of the form `~ g1 + ... + gk` to split by the interaction of the variables `g1, ..., gk`. This parameter is passed directly into `split()` function.
`FUN`	(`function`) the function to be applied to each subset of `df` defined by `f`.
`...`	parameters passed to `lapply()`, which is used when applying a function `FUN` over groups defined by `f`.

The data.frame object with results from FUN.

df <- data.frame(
  dose = c(0.1, 6, 6, 5, 0.1, 5, 6, 6),
  cohort = c("B", "B", "B", "A", "A", "A", "B", "B")
)

dapply(
  df,
  f = ~cohort,
  FUN = function(coh) {
    data.frame(my_cohort = coh$cohort[1], my_max = max(coh$dose))
  }
)

dapply(
  df,
  f = ~cohort,
  FUN = function(coh) {
    coh$dose <- sort(coh$dose, decreasing = TRUE)
    coh
  }
)