Searching functions using grep over multiple loaded packages in R

To get a list of all packages which are loaded, use:

x <- grep('package:',search(),value=TRUE)  # Comment below by danielson
# e.g. ("package:base", "package:data.table")

sapply(x, function(x) {
    paste0(x, ":", grep("is\\.", ls(x),value=TRUE))
})

Output:

$`package:base`
 [1] "package:base:is.array"              "package:base:is.atomic"
 [3] "package:base:is.call"               "package:base:is.character"
 [5] "package:base:is.complex"            "package:base:is.data.frame"
 [7] "package:base:is.double"             "package:base:is.element"
 ...

$`package:data.table`
[1] "package:data.table:is.data.table"