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copied!<p>In R every "object" has a <code>mode</code> and a <code>class</code>. The former represents how an object is stored in memory (numeric, character, list and function) while the later represents its abstract type. For example:</p> <pre><code>d <- data.frame(V1=c(1,2)) class(d) # [1] "data.frame" mode(d) # [1] "list" typeof(d) # list </code></pre> <p>As you can see data frames are stored in memory as <code>list</code> but they are wrapped into <code>data.frame</code> objects. The latter allows for usage of member functions as well as overloading functions such as <code>print</code> with a custom behavior. </p> <p><code>typeof</code>(<code>storage.mode</code>) will usually give the same information as <code>mode</code> but not always. Case in point:</p> <pre><code>typeof(c(1,2)) # [1] "double" mode(c(1,2)) # [1] "numeric" </code></pre> <p>The reasoning behind this can be found <a href="http://stat.ethz.ch/R-manual/R-devel/doc/manual/R-lang.html#Objects">here</a>:</p> <blockquote> <p>The R specific function <strong>typeof</strong> returns the type of an R object</p> <p>Function <strong>mode</strong> gives information about the mode of an object in the sense of Becker, Chambers & Wilks (1988), and is more compatible with other implementations of the S language</p> </blockquote> <p>The link that I posted above also contains a list of all native R <code>basic types</code> (vectors, lists etc.) and all <code>compound objects</code> (factors and data.frames) as well as some examples of how <code>mode</code>, <code>typeof</code> and <code>class</code> are related for each type.</p>

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