Rdpack (version 0.4-4)

Rdo_locate: Find positions of elements in an Rd object

Description

Find positions of elements for which a function returns TRUE. Along with the positions return, optionally, the results of applying another function to the selected elements.

Usage

Rdo_locate(object, f = function(x) TRUE, pos_only = TRUE,
           lists = FALSE, fpos = NULL, nested = TRUE)

Arguments

object

an Rd object

f

a function returning TRUE if an element is desired and FALSE otherwise.

pos_only

if TRUE, return only the positions; if this argument is a function, return also the result of applying the function to the selected element, see Details.

lists

if FALSE, examine only leaves, if TRUE, examine also lists, see Details.

fpos

a function with two arguments, object and position, it is called and the value is returned along with the position, see Details.

nested

a logical value, it has effect only when lists is TRUE, see `Details'.

Value

• a list with one entry for each selected element. Each entry is a numeric vector or a list with two elements:
• pos
  the position, a vector of positive integers,
• value
  the result of applying the function to this element.

Details

With the default setting of lists = FALSE, the function f is applied to each leave (a character string) of the Rd object. If lists = TRUE the function f is applied also to each branch (a list). In this case, argument nested controls what happens when f returns TRUE. If nested is TRUE, each element of the list is also inspected recursively, otherwise this is not done and effectively, the list is considered a leave. If f does not return TRUE, the value of nested has no effect and the elements of the list are inspected. The position of each object for which f returns TRUE is recorded as a numeric vector. If fpos is a function, it is applied to each selected element with two arguments, object and the position, and the result returned along with the position. In this case argument pos_only is ignored. If fpos is NULL the action depends on pos_only. If pos_only = TRUE, Rdo_locate returns a list of such vectors (it is not a matrix since the positions of the leaves are, in general, at different depths). If pos_only is a function, it is applied to each selected element and the result returned along with the position. Argument fpos is more powerful than pos_only but the latter should be sufficient and simpler to use in most cases.