Analyzing foreign source code in R - How can I find functions / operators that are hard to google?

Question

Trying to learn something from source code. I stumbled upon "%||%" in ggplot2 as well as in rCharts. Obviously the latter does not import the former, nor does it define "%||%" as a function. How can I search my R ecosystem for these functions? OS X' spotlight seems not to be the easiest solution.

Can anybody explain what it does and point to where it's defined?

No, I didn't. Thanks! Is it the same that rCharts uses? Because I was looking at rCharts and could not find where it gets the definition from because it does not import ggplot2 — Matt Bannert, Sep 14 '13 at 10:26

score 5 · Accepted Answer · edited Sep 14 '13 at 10:45

5

In both of these cases, the function does the same thing.

Here it is from rCharts:

#' Set a default value for an object
#' 
#' This function sets the value of an object to a default value if it is not defined. 
#' @params x object
#' @params y object
#' @keywords internal
#' @noRd
`%||%` <- function(x, y){
  if (is.null(x)) y else x
}

Here it is from "ggplot2"--slightly different syntax but same operation:

ggplot2:::`%||%`
# function (a, b) 
# {
#     if (!is.null(a)) 
#         a
#     else b
# }

For finding the definitions of these functions, you can start by trying getAnywhere(). Here's the result on my system:

getAnywhere("%||%")
# 3 differing objects matching ‘%||%’ were found
# in the following places
#   namespace:ggplot2
#   namespace:gtable
#   namespace:plyr
#   namespace:reshape2
#   namespace:scales
# Use [] to view one of them

Edit: note that [] accepts numeric arguments, not the package names

edited Sep 14 '13 at 10:45

Matt Bannert

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answered Sep 14 '13 at 10:27

A5C1D2H2I1M1N2O1R2T1

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sorry for being so blind, which file is it? – Matt Bannert Sep 14 '13 at 10:28
sorry, not my really a good start of the day. Thanks for helping out though. – Matt Bannert Sep 14 '13 at 10:29
1

@MattBannert, no problem. I even highlighted the relevant lines for you in the link :) – A5C1D2H2I1M1N2O1R2T1 Sep 14 '13 at 10:30
I just thought, it's the link to the github repo that I know anyway. It seems that I am slowly gettin' my head around github's features. – Matt Bannert Sep 14 '13 at 10:32
1

OK. I added another little tip for you @MattBannert. – A5C1D2H2I1M1N2O1R2T1 Sep 14 '13 at 10:37
@AnandaMahto, a quick follow-up: when accessing internal variables using triple colon `:::`, does it ever matter if you use backticks `` or double quotes `""` around the function name. I just tried `ggplot2:::"%||%"` which works, but is it always the case? +1 for a great explanation. Cheers. – Henrik Sep 14 '13 at 10:41
@AnandaMahto very helpful tips I re-worded the original questions so others might find these tips more easily. – Matt Bannert Sep 14 '13 at 10:44
@Henrik, See the last paragraph of `?Quotes` for why I've used backticks (`\``). – A5C1D2H2I1M1N2O1R2T1 Sep 14 '13 at 10:45

Analyzing foreign source code in R - How can I find functions / operators that are hard to google?

1 Answers1