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POHow can I reference the local environment within a function, in R?
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copied!<p>[This question has been resolved in the <a href="http://chat.stackoverflow.com/transcript/message/2307138#2307138">chat room, by Spacedman</a>, but I'm posting it for others' benefit in the future.]</p> <p>I have a function, <code>myFunc</code>, which creates <code>localFunc</code> inside of it. (NB: this is not in a package, but in the global environment.) I'd like to know where <code>localFunc</code> exists in the search path, as I'd like to analyze it via <code>mvbutils::foodweb</code>.</p> <p>Here is an example:</p> <pre><code>myFunc <- function(){ require(data.table) require(mvbutils) localFunc <- function(x){ return(as.data.table(x)) } vecPrune <- c("localFunc",ls("package:data.table")) ix <- match("data.table",search()) tmpWeb <- foodweb(where = c(1,ix), prune = vecPrune, plotting = FALSE) return(tmpWeb) } </code></pre> <p>However, a call to <code>myFunc()</code> does not seem to indicate that <code>localFunc</code> calls <code>data.table()</code>. This is incorrect - what gives?</p> <p>(NB: The <code>where</code> argument specifies the search path.)</p> <hr> <p>Update 1: As Tommy and Spacedman point out, the trick is to specify <code>environment()</code>. The call to <code>foodweb()</code> refers to <code>where = c(1, ix)</code>. The index <code>1</code> is a mistake. That arose from thinking that <code>.GlobalEnv</code>, which is often (always?) the first item in the <code>search()</code> vector, is the right place to search. That is erroneous. Instead, one should refer to <code>environment()</code>, and the correct call is below. (NB: <code>ix</code> specifies the location of <code>data.table()</code> in the <code>search()</code> output.) </p> <pre><code>tmpWeb <- foodweb(where = c(environment(),ix), prune = vecPrune, plotting = FALSE) </code></pre> <p>This appears in the answer to <a href="https://stackoverflow.com/a/8777882/805808">this question</a>, in a function called <code>checkScriptDependencies</code>, which wraps the code from an R script file into a local function, which is then analyzed by <code>foodweb</code>. This is a limited example of how to use <code>environment()</code>, and Tommy has given a good explanation of how to use it and similar functions in this context.</p>

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