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POWhy this behavior when coercing a list to character via as.character()?
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  1. POWhy this behavior when coercing a list to character via as.character()?
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    copied!<p>In the process of (mostly) answering <a href="https://stackoverflow.com/q/7591295/324364">this</a> question, I stumbled across something that I feel like I really should already have seen before. Let's say you've got a list:</p> <pre><code>l &lt;- list(a = 1:3, b = letters[1:3], c = runif(3)) </code></pre> <p>Attempting to coerce <code>l</code> to various types returns an error:</p> <pre><code>&gt; as.numeric(l) Error: (list) object cannot be coerced to type 'double' &gt; as.logical(l) Error: (list) object cannot be coerced to type 'logical' </code></pre> <p>However, I'm apparently allowed to coerce a list to character, I just wasn't expecting this result:</p> <pre><code>&gt; as.character(l) [1] "1:3" [2] "c(\"a\", \"b\", \"c\")" [3] "c(0.874045701464638, 0.0843329173512757, 0.809434881201014)" </code></pre> <p>Rather, if I'm allowed to coerce lists to character, I would have thought I'd see behavior more like this:</p> <pre><code>&gt; as.character(unlist(l)) [1] "1" "2" "3" "a" "b" [6] "c" "0.874045701464638" "0.0843329173512757" "0.809434881201014" </code></pre> <p>Note that <em>how I specify the list elements originally</em> affects the output of <code>as.character</code>:</p> <pre><code>l &lt;- list(a = c(1,2,3), b = letters[1:3], c = runif(3)) &gt; as.character(l) [1] "c(1, 2, 3)" [2] "c(\"a\", \"b\", \"c\")" [3] "c(0.344991483259946, 0.0492411875165999, 0.625746068544686)" </code></pre> <p>I have two questions:</p> <ol> <li>How is <code>as.character</code> dredging up the information from my original creation of the list <code>l</code> in order to spit out <code>1:3</code> versus <code>c(1,2,3)</code>.</li> <li>In what circumstances would I want to do this, exactly? When would I want to call <code>as.character()</code> on a list and get output of this form?</li> </ol>
 

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