drop.levels.html
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html><head><title>R: Drop unused factor levels</title>
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<table width="100%" summary="page for drop.levels {gdata}"><tr><td>drop.levels {gdata}</td><td align="right">R Documentation</td></tr></table>
<h2>Drop unused factor levels</h2>
<h3>Description</h3>
<p>
Drop unused levels in a factor.
</p>
<h3>Usage</h3>
<pre>
drop.levels(x, reorder=TRUE, ...)
</pre>
<h3>Arguments</h3>
<table summary="R argblock">
<tr valign="top"><td><code>x</code></td>
<td>
object to be processed</td></tr>
<tr valign="top"><td><code>reorder</code></td>
<td>
should factor levels be reordered using
<code><a href="reorder.html">reorder.factor</a></code>?</td></tr>
<tr valign="top"><td><code>...</code></td>
<td>
additional arguments to <code>reorder.factor</code></td></tr>
</table>
<h3>Details</h3>
<p>
<code>drop.levels</code> is a generic function, where default method does
nothing, while method for factor <code>s</code> drops all unused levels. There
are also convinient methods for <code>list</code> and <code>data.frame</code>, where
all unused levels are droped in all factors (one by one) in a
<code>list</code> or a <code>data.frame</code>.
</p>
<h3>Value</h3>
<p>
a data frame</p>
<h3>Author(s)</h3>
<p>
Jim Rogers <a href="mailto:james.a.rogers@pfizer.com">james.a.rogers@pfizer.com</a>
</p>
<h3>Examples</h3>
<pre>
f <- factor(c("A", "B", "C", "D"))[1:3]
drop.levels(f)
l <- list(f=f, i=1:3, c=c("A", "B", "D"))
drop.levels(l)
df <- as.data.frame(l)
str(df)
str(drop.levels(df))
</pre>
<hr><div align="center">[Package <em>gdata</em> version 2.3.1 <a href="00Index.html">Index]</a></div>
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