fapply {autoharp}

Apply a function to a forest of trees.

Description

A convenience function, for applying a function to many trees.

Usage

fapply(fharp, TFUN, combine = TRUE, combiner_fn, ...)

Arguments

fharp

The output of rmd_to_forestharp. It could also just be a list of TreeHarp objects.

TFUN

A function that works on a single TreeHarp and returns an output. See forestharp-helpers for examples.

combine

A logical value that indicates if the output from all function applications should be combined.

combiner_fn

A function to use to combine the individual output from each tree into a single scalar for each forest. It should handle NA values in the input vector or list. If it is missing, it defaults to sum, with na.rm=TRUE.

...

Additional arguments to be passed on to TFUN.

Details

The input is simply a list of TreeHarp objects. First, the TFUN function is lapply-ed to each TreeHarp item, resulting in either a list, or a vector with possible NA elements.

The combiner function should be aware of this sort of output, and summarise the list or vector accordingly, handling NA's and returning a scalar.

If you need to create a partial function out of a forestharp helper, use an anonymous function, as shown in the examples below.

Value

A vector, list or a single value. If TFUN returned an error for a particular TreeHarp, that component in the list or vector would be NA. This input vector or list will then be combined by combiner_fn.

Examples

ex1 <- quote(X <- rnorm(10, mean=0.9, sd=4))
ex2 <- quote(Y <- rbeta(10, shape1=3, shape2=5))
f1 <- lapply(c(ex1, ex2), TreeHarp, quote_arg=TRUE) 

# returns all function calls that begin with "r", like rnorm and rbeta.
# calls are returned as a list.
fapply(f1, extract_fn_call, combine =FALSE, pattern="^r.*")

# list is catenated.
fapply(f1, extract_fn_call, combine =TRUE, pattern="^r.*", 
       combiner_fn = function(x) {paste0(unlist(x), collapse=",")})