Searching functions using grep over multiple loaded packages in R

Question

Lets say I have package base, dplyr, data.table, tidyr etc. loaded using sapply().

 sapply(c("dplyr","data.table","tidyr"),library,character.only=TRUE)

So to check the list of functions in a particular package I do

 ls("package:data.table")

Now if I want to search for functions inside dplyr starting with is. pattern I do

 grep("is\\.",ls("package:dplyr"),value=TRUE)
 # [1] "is.grouped_df" "is.ident"      "is.sql"        "is.src"       
 # [5] "is.tbl" 

My Goal is to search for all the functions starting with is. or as. or any other pattern in multiple packages simultaneously. The code I think would be lengthy i.e. below I have combined list of dplyr and base functions and then added grep pattern. How to do it for many loaded packages?

 grep("is\\.",c(ls("package:dplyr"),ls("package:base")),value=T)

Function search() would give me list of loaded packages. But how to gather all the functions of loaded packages, so that I can later grep on it.

For a single package, list of functions can be obtained by

 ls("package:package_name")  

Any help is highly appreciated.

Answer 1

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"