zfunction {zfit}

Create a pipe-friendly version of a function

Description

These functions all serve the role of rearranging the arguments of other functions, in order to create pipe-friendly versions.

zfunction() rearranges the arguments of any function moving the specified argument to the front of the list, so that this argument becomes the recipient of piping. It returns a copy of the input function, that is identical to the original except for the order of the arguments.

zfold() creates a pipe-friendly version of a function of the standard format by creating a fold (or wrapper) around it with the parameters reordered. Compared to using zfunction(), which makes a copy of the original function with rearranged the parameters, this creates a wrapper that in turn will call the original function with all passed parameters. This is good for making pipe-friendly versions of S3 generics, whereas rearranging parameters directly will break the S3 dispatch mechanism.

zfitter() creates a pipe-friendly version of a fitting function of the standard format –– that is a function with a formula parameter followed by a data parameter. It also shortens very long data names (longer than 32 characters by default), which otherwise are a nuisance when the data comes from the pipe, because the pipeline gets converted to a very long function call.

Usage

zfunction(fun, x, x_not_found = c("error", "warning", "ok"))

zfold(fun, x, x_not_found = c("error", "warning", "ok"))

zfitter(fun)

Arguments

fun

The function to adapt (for zfitter() this should be a fitting function that takes formula and data parameters). The name should not be quoted, rather, the actual function should be passed (prefixed with package if needed).

x

The name of the argument that should be moved to the front of the argument list. Can be passed with or without quotes, and is processed using non-standard evaluation unless surrounded with curlies, as in {value}, see details below.

x_not_found

How to handle the case where the value of x is not the name of a parameter in fun. If error, abort the function. If ok, prepend the value to the existing parameter list. This can be useful if looking to pipe data into a parameter that is hidden by a ....

Details

The x parameter is processed using non-standard evaluation, which can be disabled using curly brackets. In other words, the following are all equivalent, and return a file renaming function with the to parameter as the first one:

• zfunction(file.rename, to)

• zfunction(file.rename, "to")

• ⁠param_name <- "to"; zfunction(file.rename, {param_name})⁠

Examples

# A a grep function with x as first param is often useful
zgrep <- zfunction(grep, x)
carnames <- rownames(mtcars)
grep("ll", carnames, value=TRUE)
zgrep(carnames, "ll", value=TRUE)

# zfunction() is the best approach to wrapping functions such as
# `pls::plsr()` that hide the data parameter behind the `...`.
if (requireNamespace("pls")) {
  zplsr <- zfunction(pls::plsr, data, x_not_found = "ok")
  zplsr(cars, dist ~ speed)
}

# Curly {x} handling: These are all equivalent
param_name <- "to";
f1 <- zfunction(file.rename, to)
f2 <- zfunction(file.rename, "to")
f3 <- zfunction(file.rename, {param_name})

# Using zfold() to create a grep() wrapper with the desired arg order
zgrep <- zfold(grep, x)
carnames <- rownames(mtcars)
grep("ll", carnames, value=TRUE)
zgrep(carnames, "ll", value=TRUE)

# Using zfitter to wrap around a fitting function
# (this is the actual way zlm_robust is defined in this package)
if (requireNamespace("estimatr", quietly = TRUE)) {
  zlm_robust <- zfitter(estimatr::lm_robust)
  zlm_robust(cars, speed~dist)

  # The resulting function works well the native pipe ...
  if ( getRversion() >= "4.1.0" ) {
    cars |> zlm_robust( speed ~ dist )
  }
}

# ... or with dplyr
if ( require("dplyr", warn.conflicts=FALSE) ) {

  # Pipe cars dataset into zlm_robust for fitting
  cars %>% zlm_robust( speed ~ dist )

  # Process iris with filter() before piping. Print a summary()
  # of the fitted model using zprint() before assigning the
  # model itself (not the summary) to m.
  m <- iris %>%
    dplyr::filter(Species=="setosa") %>%
    zlm_robust(Sepal.Length ~ Sepal.Width + Petal.Width) %>%
    zprint(summary)
}