R: Recursively Modify Elements of a List

modifyList {utils} | R Documentation

## Recursively Modify Elements of a List

### Description

Modifies a possibly nested list recursively by changing a subset of elements at each level to match a second list.

### Usage

    modifyList(x, val, keep.null = FALSE)

### Arguments

`x` | A named `list`, possibly empty.
`val` | A named list with components to replace corresponding components in `x`.
`keep.null` | If `TRUE`, `NULL` elements in `val` become `NULL` elements in `x`. Otherwise, the corresponding element, if present, is deleted from `x`.

### Value

A modified version of `x`, with the modifications determined as follows (here, list elements are identified by their names). Elements in `val` which are missing from `x` are added to `x`. For elements that are common to both but are not both lists themselves, the component in `x` is replaced (or possibly deleted, depending on the value of `keep.null`) by the one in `val`. For common elements that are in both lists, `x[[name]]` is replaced by `modifyList(x[[name]], val[[name]])`.

### Author(s)

Deepayan Sarkar Deepayan.Sarkar@R-project.org

### Examples

    foo <- list(a = 1, b = list(c = "a", d = FALSE))
    bar <- modifyList(foo, list(e = 2, b = list(d = TRUE)))
    str(foo)
    str(bar)

[Package utils version 3.1.2 Index]