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| |
| <h1>Array Classes</h1> |
| <small class="dont-index">Source: <a href="https://github.com/apache/arrow/blob/main/r/R/array.R" class="external-link"><code>R/array.R</code></a></small> |
| <div class="d-none name"><code>array-class.Rd</code></div> |
| </div> |
| |
| <div class="ref-description section level2"> |
| <p>An <code>Array</code> is an immutable data array with some logical type |
| and some length. Most logical types are contained in the base |
| <code>Array</code> class; there are also subclasses for <code>DictionaryArray</code>, <code>ListArray</code>, |
| and <code>StructArray</code>.</p> |
| </div> |
| |
| |
| <div class="section level2"> |
| <h2 id="factory">Factory<a class="anchor" aria-label="anchor" href="#factory"></a></h2> |
| |
| |
| <p>The <code>Array$create()</code> factory method instantiates an <code>Array</code> and |
| takes the following arguments:</p><ul><li><p><code>x</code>: an R vector, list, or <code>data.frame</code></p></li> |
| <li><p><code>type</code>: an optional <a href="data-type.html">data type</a> for <code>x</code>. If omitted, the type |
| will be inferred from the data.</p></li> |
| </ul><p><code>Array$create()</code> will return the appropriate subclass of <code>Array</code>, such as |
| <code>DictionaryArray</code> when given an R factor.</p> |
| <p>To compose a <code>DictionaryArray</code> directly, call <code>DictionaryArray$create()</code>, |
| which takes two arguments:</p><ul><li><p><code>x</code>: an R vector or <code>Array</code> of integers for the dictionary indices</p></li> |
| <li><p><code>dict</code>: an R vector or <code>Array</code> of dictionary values (like R factor levels |
| but not limited to strings only)</p></li> |
| </ul></div> |
| <div class="section level2"> |
| <h2 id="usage">Usage<a class="anchor" aria-label="anchor" href="#usage"></a></h2> |
| |
| |
| |
| <p></p><div class="sourceCode"><pre><code><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a>a <span class="ot"><-</span> Array<span class="sc">$</span><span class="fu">create</span>(x)</span> |
| <span id="cb1-2"><a href="#cb1-2" aria-hidden="true" tabindex="-1"></a><span class="fu">length</span>(a)</span> |
| <span id="cb1-3"><a href="#cb1-3" aria-hidden="true" tabindex="-1"></a></span> |
| <span id="cb1-4"><a href="#cb1-4" aria-hidden="true" tabindex="-1"></a><span class="fu">print</span>(a)</span> |
| <span id="cb1-5"><a href="#cb1-5" aria-hidden="true" tabindex="-1"></a>a <span class="sc">==</span> a</span></code></pre><p></p></div> |
| </div> |
| <div class="section level2"> |
| <h2 id="methods">Methods<a class="anchor" aria-label="anchor" href="#methods"></a></h2> |
| |
| |
| <ul><li><p><code>$IsNull(i)</code>: Return true if value at index is null. Does not boundscheck</p></li> |
| <li><p><code>$IsValid(i)</code>: Return true if value at index is valid. Does not boundscheck</p></li> |
| <li><p><code>$length()</code>: Size in the number of elements this array contains</p></li> |
| <li><p><code>$nbytes()</code>: Total number of bytes consumed by the elements of the array</p></li> |
| <li><p><code>$offset</code>: A relative position into another array's data, to enable zero-copy slicing</p></li> |
| <li><p><code>$null_count</code>: The number of null entries in the array</p></li> |
| <li><p><code>$type</code>: logical type of data</p></li> |
| <li><p><code>$type_id()</code>: type id</p></li> |
| <li><p><code>$Equals(other)</code> : is this array equal to <code>other</code></p></li> |
| <li><p><code>$ApproxEquals(other)</code> :</p></li> |
| <li><p><code>$Diff(other)</code> : return a string expressing the difference between two arrays</p></li> |
| <li><p><code>$data()</code>: return the underlying <a href="ArrayData.html">ArrayData</a></p></li> |
| <li><p><code>$as_vector()</code>: convert to an R vector</p></li> |
| <li><p><code>$ToString()</code>: string representation of the array</p></li> |
| <li><p><code>$Slice(offset, length = NULL)</code>: Construct a zero-copy slice of the array |
| with the indicated offset and length. If length is <code>NULL</code>, the slice goes |
| until the end of the array.</p></li> |
| <li><p><code>$Take(i)</code>: return an <code>Array</code> with values at positions given by integers |
| (R vector or Array Array) <code>i</code>.</p></li> |
| <li><p><code>$Filter(i, keep_na = TRUE)</code>: return an <code>Array</code> with values at positions where logical |
| vector (or Arrow boolean Array) <code>i</code> is <code>TRUE</code>.</p></li> |
| <li><p><code>$SortIndices(descending = FALSE)</code>: return an <code>Array</code> of integer positions that can be |
| used to rearrange the <code>Array</code> in ascending or descending order</p></li> |
| <li><p><code>$RangeEquals(other, start_idx, end_idx, other_start_idx)</code> :</p></li> |
| <li><p><code>$cast(target_type, safe = TRUE, options = cast_options(safe))</code>: Alter the |
| data in the array to change its type.</p></li> |
| <li><p><code>$View(type)</code>: Construct a zero-copy view of this array with the given type.</p></li> |
| <li><p><code>$Validate()</code> : Perform any validation checks to determine obvious inconsistencies |
| within the array's internal data. This can be an expensive check, potentially <code>O(length)</code></p></li> |
| </ul></div> |
| |
| <div class="section level2"> |
| <h2 id="ref-examples">Examples<a class="anchor" aria-label="anchor" href="#ref-examples"></a></h2> |
| <div class="sourceCode"><pre class="sourceCode r"><code><span class="r-in"><span><span class="va">my_array</span> <span class="op"><-</span> <span class="va">Array</span><span class="op">$</span><span class="fu">create</span><span class="op">(</span><span class="fl">1</span><span class="op">:</span><span class="fl">10</span><span class="op">)</span></span></span> |
| <span class="r-in"><span><span class="va">my_array</span><span class="op">$</span><span class="va">type</span></span></span> |
| <span class="r-out co"><span class="r-pr">#></span> Int32</span> |
| <span class="r-out co"><span class="r-pr">#></span> int32</span> |
| <span class="r-in"><span><span class="va">my_array</span><span class="op">$</span><span class="fu">cast</span><span class="op">(</span><span class="fu"><a href="data-type.html">int8</a></span><span class="op">(</span><span class="op">)</span><span class="op">)</span></span></span> |
| <span class="r-out co"><span class="r-pr">#></span> Array</span> |
| <span class="r-out co"><span class="r-pr">#></span> <int8></span> |
| <span class="r-out co"><span class="r-pr">#></span> [</span> |
| <span class="r-out co"><span class="r-pr">#></span> 1,</span> |
| <span class="r-out co"><span class="r-pr">#></span> 2,</span> |
| <span class="r-out co"><span class="r-pr">#></span> 3,</span> |
| <span class="r-out co"><span class="r-pr">#></span> 4,</span> |
| <span class="r-out co"><span class="r-pr">#></span> 5,</span> |
| <span class="r-out co"><span class="r-pr">#></span> 6,</span> |
| <span class="r-out co"><span class="r-pr">#></span> 7,</span> |
| <span class="r-out co"><span class="r-pr">#></span> 8,</span> |
| <span class="r-out co"><span class="r-pr">#></span> 9,</span> |
| <span class="r-out co"><span class="r-pr">#></span> 10</span> |
| <span class="r-out co"><span class="r-pr">#></span> ]</span> |
| <span class="r-in"><span></span></span> |
| <span class="r-in"><span><span class="co"># Check if value is null; zero-indexed</span></span></span> |
| <span class="r-in"><span><span class="va">na_array</span> <span class="op"><-</span> <span class="va">Array</span><span class="op">$</span><span class="fu">create</span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/base/c.html" class="external-link">c</a></span><span class="op">(</span><span class="fl">1</span><span class="op">:</span><span class="fl">5</span>, <span class="cn">NA</span><span class="op">)</span><span class="op">)</span></span></span> |
| <span class="r-in"><span><span class="va">na_array</span><span class="op">$</span><span class="fu">IsNull</span><span class="op">(</span><span class="fl">0</span><span class="op">)</span></span></span> |
| <span class="r-out co"><span class="r-pr">#></span> [1] FALSE</span> |
| <span class="r-in"><span><span class="va">na_array</span><span class="op">$</span><span class="fu">IsNull</span><span class="op">(</span><span class="fl">5</span><span class="op">)</span></span></span> |
| <span class="r-out co"><span class="r-pr">#></span> [1] TRUE</span> |
| <span class="r-in"><span><span class="va">na_array</span><span class="op">$</span><span class="fu">IsValid</span><span class="op">(</span><span class="fl">5</span><span class="op">)</span></span></span> |
| <span class="r-out co"><span class="r-pr">#></span> [1] FALSE</span> |
| <span class="r-in"><span><span class="va">na_array</span><span class="op">$</span><span class="va">null_count</span></span></span> |
| <span class="r-out co"><span class="r-pr">#></span> [1] 1</span> |
| <span class="r-in"><span></span></span> |
| <span class="r-in"><span><span class="co"># zero-copy slicing; the offset of the new Array will be the same as the index passed to $Slice</span></span></span> |
| <span class="r-in"><span><span class="va">new_array</span> <span class="op"><-</span> <span class="va">na_array</span><span class="op">$</span><span class="fu">Slice</span><span class="op">(</span><span class="fl">5</span><span class="op">)</span></span></span> |
| <span class="r-in"><span><span class="va">new_array</span><span class="op">$</span><span class="va">offset</span></span></span> |
| <span class="r-out co"><span class="r-pr">#></span> [1] 5</span> |
| <span class="r-in"><span></span></span> |
| <span class="r-in"><span><span class="co"># Compare 2 arrays</span></span></span> |
| <span class="r-in"><span><span class="va">na_array2</span> <span class="op"><-</span> <span class="va">na_array</span></span></span> |
| <span class="r-in"><span><span class="va">na_array2</span> <span class="op">==</span> <span class="va">na_array</span> <span class="co"># element-wise comparison</span></span></span> |
| <span class="r-out co"><span class="r-pr">#></span> Array</span> |
| <span class="r-out co"><span class="r-pr">#></span> <bool></span> |
| <span class="r-out co"><span class="r-pr">#></span> [</span> |
| <span class="r-out co"><span class="r-pr">#></span> true,</span> |
| <span class="r-out co"><span class="r-pr">#></span> true,</span> |
| <span class="r-out co"><span class="r-pr">#></span> true,</span> |
| <span class="r-out co"><span class="r-pr">#></span> true,</span> |
| <span class="r-out co"><span class="r-pr">#></span> true,</span> |
| <span class="r-out co"><span class="r-pr">#></span> null</span> |
| <span class="r-out co"><span class="r-pr">#></span> ]</span> |
| <span class="r-in"><span><span class="va">na_array2</span><span class="op">$</span><span class="fu">Equals</span><span class="op">(</span><span class="va">na_array</span><span class="op">)</span> <span class="co"># overall comparison</span></span></span> |
| <span class="r-out co"><span class="r-pr">#></span> [1] TRUE</span> |
| </code></pre></div> |
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