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PODisable assignment via = in R
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copied!<p>R allows for assignment via <code><-</code> and <code>=</code>.</p> <p>Whereas there a <a href="https://stackoverflow.com/q/1741820/289572">subtle differences</a> between both assignment operators, there seems to be a broad consensus that <code><-</code> is the better choice than <code>=</code>, as <code>=</code> is also used as operator mapping values to arguments and thus its use may lead to ambiguous statements. The following exemplifies this:</p> <pre><code>> system.time(x <- rnorm(10)) user system elapsed 0 0 0 > system.time(x = rnorm(10)) Error in system.time(x = rnorm(10)) : unused argument(s) (x = rnorm(10)) </code></pre> <p>In fact, the <a href="http://google-styleguide.googlecode.com/svn/trunk/google-r-style.html#assignment" rel="nofollow noreferrer">Google style code</a> disallows using <code>=</code> for assignment (see comments to this <a href="https://stackoverflow.com/a/1742591/289572">answer</a> for a converse view).</p> <p>I also almost exclusively use <code><-</code> as assignment operator. However, the almost in the previous sentence is the reason for this question. When <code>=</code> acts as assignment operator in my code it is always accidental and if it leads to problems these are usually hard to spot.</p> <p><strong>I would like to know if there is a way to turn off assignment via <code>=</code> and let R throw an error any time <code>=</code> is used for assignment.</strong></p> <p>Optimally this behavior would only occur for code in the Global Environment, as there may well be code in attached namespaces that uses <code>=</code> for assignment and should not break.</p> <p>(This question was inspired by a discussion with <a href="http://www.jonathandnelson.com/" rel="nofollow noreferrer">Jonathan Nelson</a>)</p>

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