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| included in a Dataset. There are subclasses corresponding to the supported |
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| <img src="" class="logo" alt=""><h1>Dataset file formats</h1> |
| <small class="dont-index">Source: <a href="https://github.com/apache/arrow/blob/master/r/R/dataset-format.R" class="external-link"><code>R/dataset-format.R</code></a></small> |
| <div class="d-none name"><code>FileFormat.Rd</code></div> |
| </div> |
| |
| <div class="ref-description section level2"> |
| <p>A <code>FileFormat</code> holds information about how to read and parse the files |
| included in a <code>Dataset</code>. There are subclasses corresponding to the supported |
| file formats (<code>ParquetFileFormat</code> and <code>IpcFileFormat</code>).</p> |
| </div> |
| |
| |
| <div class="section level2"> |
| <h2 id="factory">Factory<a class="anchor" aria-label="anchor" href="#factory"></a></h2> |
| |
| |
| <p><code>FileFormat$create()</code> takes the following arguments:</p><ul><li><p><code>format</code>: A string identifier of the file format. Currently supported values:</p><ul><li><p>"parquet"</p></li> |
| <li><p>"ipc"/"arrow"/"feather", all aliases for each other; for Feather, note that |
| only version 2 files are supported</p></li> |
| <li><p>"csv"/"text", aliases for the same thing (because comma is the default |
| delimiter for text files</p></li> |
| <li><p>"tsv", equivalent to passing <code>format = "text", delimiter = "\t"</code></p></li> |
| </ul></li> |
| <li><p><code>...</code>: Additional format-specific options</p> |
| <p>`format = "parquet"``:</p><ul><li><p><code>dict_columns</code>: Names of columns which should be read as dictionaries.</p></li> |
| <li><p>Any Parquet options from <a href="FragmentScanOptions.html">FragmentScanOptions</a>.</p></li> |
| </ul><p><code>format = "text"</code>: see <a href="CsvReadOptions.html">CsvParseOptions</a>. Note that you can specify them either |
| with the Arrow C++ library naming ("delimiter", "quoting", etc.) or the |
| <code>readr</code>-style naming used in <code><a href="read_delim_arrow.html">read_csv_arrow()</a></code> ("delim", "quote", etc.). |
| Not all <code>readr</code> options are currently supported; please file an issue if |
| you encounter one that <code>arrow</code> should support. Also, the following options are |
| supported. From <a href="CsvReadOptions.html">CsvReadOptions</a>:</p><ul><li><p><code>skip_rows</code></p></li> |
| <li><p><code>column_names</code>. Note that if a <a href="Schema.html">Schema</a> is specified, <code>column_names</code> must match those specified in the schema.</p></li> |
| <li><p><code>autogenerate_column_names</code> |
| From <a href="FragmentScanOptions.html">CsvFragmentScanOptions</a> (these values can be overridden at scan time):</p></li> |
| <li><p><code>convert_options</code>: a <a href="CsvReadOptions.html">CsvConvertOptions</a></p></li> |
| <li><p><code>block_size</code></p></li> |
| </ul></li> |
| </ul><p>It returns the appropriate subclass of <code>FileFormat</code> (e.g. <code>ParquetFileFormat</code>)</p> |
| </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="co">## Semi-colon delimited files</span></span></span> |
| <span class="r-in"><span><span class="co"># Set up directory for examples</span></span></span> |
| <span class="r-in"><span><span class="va">tf</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/tempfile.html" class="external-link">tempfile</a></span><span class="op">(</span><span class="op">)</span></span></span> |
| <span class="r-in"><span><span class="fu"><a href="https://rdrr.io/r/base/files2.html" class="external-link">dir.create</a></span><span class="op">(</span><span class="va">tf</span><span class="op">)</span></span></span> |
| <span class="r-in"><span><span class="fu"><a href="https://rdrr.io/r/base/on.exit.html" class="external-link">on.exit</a></span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/base/unlink.html" class="external-link">unlink</a></span><span class="op">(</span><span class="va">tf</span><span class="op">)</span><span class="op">)</span></span></span> |
| <span class="r-in"><span><span class="fu"><a href="https://rdrr.io/r/utils/write.table.html" class="external-link">write.table</a></span><span class="op">(</span><span class="va">mtcars</span>, <span class="fu"><a href="https://rdrr.io/r/base/file.path.html" class="external-link">file.path</a></span><span class="op">(</span><span class="va">tf</span>, <span class="st">"file1.txt"</span><span class="op">)</span>, sep <span class="op">=</span> <span class="st">";"</span>, row.names <span class="op">=</span> <span class="cn">FALSE</span><span class="op">)</span></span></span> |
| <span class="r-in"><span></span></span> |
| <span class="r-in"><span><span class="co"># Create FileFormat object</span></span></span> |
| <span class="r-in"><span><span class="va">format</span> <span class="op"><-</span> <span class="va">FileFormat</span><span class="op">$</span><span class="fu">create</span><span class="op">(</span>format <span class="op">=</span> <span class="st">"text"</span>, delimiter <span class="op">=</span> <span class="st">";"</span><span class="op">)</span></span></span> |
| <span class="r-in"><span></span></span> |
| <span class="r-in"><span><span class="fu"><a href="open_dataset.html">open_dataset</a></span><span class="op">(</span><span class="va">tf</span>, format <span class="op">=</span> <span class="va">format</span><span class="op">)</span></span></span> |
| <span class="r-out co"><span class="r-pr">#></span> FileSystemDataset with 1 csv file</span> |
| <span class="r-out co"><span class="r-pr">#></span> mpg: double</span> |
| <span class="r-out co"><span class="r-pr">#></span> cyl: int64</span> |
| <span class="r-out co"><span class="r-pr">#></span> disp: double</span> |
| <span class="r-out co"><span class="r-pr">#></span> hp: int64</span> |
| <span class="r-out co"><span class="r-pr">#></span> drat: double</span> |
| <span class="r-out co"><span class="r-pr">#></span> wt: double</span> |
| <span class="r-out co"><span class="r-pr">#></span> qsec: double</span> |
| <span class="r-out co"><span class="r-pr">#></span> vs: int64</span> |
| <span class="r-out co"><span class="r-pr">#></span> am: int64</span> |
| <span class="r-out co"><span class="r-pr">#></span> gear: int64</span> |
| <span class="r-out co"><span class="r-pr">#></span> carb: int64</span> |
| </code></pre></div> |
| </div> |
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