Questions tagged [apply]

R

In the r language this function calls another function with a list of arguments and a defined margin to act (either 1: rows, 2: columns or c(1,2): every entry of X).

foo = apply(X = bar, MARGIN = 1, FUN = function(x) dosomething(x))

Some similar specialized functions in the *apply-family include lapply, sapply, tapply and mapply:

• lapply is a function that applies a function to each element of a list or vector. lapply returns a list.
• sapply is a function that applies a function to each element of a vector (atomic or list). It may also accept other classes if they are coercible by the function base::as.list. The sapply function returns a vector by default, however will return a list when more suitable or an array if argument simplify = "array" is specified.
• tapply is a function in the R programming language for apply a function to subsets of a vector. A vector is broken in to subsets, potentially of different lengths (aka a ragged array) based on the values of one or more other vector. The second vector is either already a factor or coerced to be a factor by as.factor. A function is applied to each of these subsets. tapply then returns either an array or a list, depending on the output of the function.
• mapply is a multivariate version of sapply. mapply applies FUN argument to the first elements of each argument, the second elements, the third elements, and so on. Arguments are recycled if necessary.

Lisp

In lisp this function calls another function with a list of arguments.

See the documentation for apply.

(apply #'- '(10 2))   ; -> 8

JavaScript

In javascript this function calls another function with the provided context and the list of arguments. A common usage:

Array.prototype.forEach.apply(document.querySelectorAll("div"), [function(element){
    // do something with "element"
}]);

The MDN documentation for apply.

Python/Pandas

Use pandas specific pandas-apply