lapply {base} R Documentation

## Apply a Function over a List or Vector

### Description

`lapply` returns a list of the same length as `X`. Each element of which is the result of applying `FUN` to the corresponding element of `X`.

`sapply` is a “user-friendly” version of `lapply` also accepting vectors as `X`, and returning a vector or matrix with `dimnames` if appropriate.

`replicate` is a wrapper for the common use of `sapply` for repeated evaluation of an expression (which will usually involve random number generation).

### Usage

```lapply(X, FUN, ...)
sapply(X, FUN, ..., simplify = TRUE, USE.NAMES = TRUE)

replicate(n, expr, simplify = TRUE)
```

### Arguments

 `X` list or vector to be used. `FUN` the function to be applied. In the case of functions like `+`, `%*%`, etc., the function name must be quoted. `...` optional arguments to `FUN`. `simplify` logical; should the result be simplified to a vector or matrix if possible? `USE.NAMES` logical; if `TRUE` and if `X` is character, use `X` as `names` for the result unless it had names already. `n` Number of replications. `expr` Expression to evaluate repeatedly.

### References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

`apply`, `tapply`.

### Examples

```x <- list(a = 1:10, beta = exp(-3:3), logic = c(TRUE,FALSE,FALSE,TRUE))
# compute the list mean for each list element
lapply(x,mean)
# median and quartiles for each list element
lapply(x, quantile, probs = 1:3/4)
sapply(x, quantile)
i39 <- sapply(3:9, seq) # list of vectors
sapply(i39, fivenum)

hist(replicate(100, mean(rexp(10))))
```

[Package base version 2.1.0 Index]