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<h1>Penlight</h1>
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<li><a href="#Functions">Functions</a></li>
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<h2>Modules</h2>
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<li><a href="../modules/config.html">config</a></li>
<li><a href="../modules/pl.html">pl</a></li>
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<li><strong>pl.data</strong></li>
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<h2>Topics</h2>
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<li><a href="../topics/01-introduction.md.html">01-introduction.md</a></li>
<li><a href="../topics/02-arrays.md.html">02-arrays.md</a></li>
<li><a href="../topics/03-strings.md.html">03-strings.md</a></li>
<li><a href="../topics/04-paths.md.html">04-paths.md</a></li>
<li><a href="../topics/05-dates.md.html">05-dates.md</a></li>
<li><a href="../topics/06-data.md.html">06-data.md</a></li>
<li><a href="../topics/07-functional.md.html">07-functional.md</a></li>
<li><a href="../topics/08-additional.md.html">08-additional.md</a></li>
<li><a href="../topics/09-discussion.md.html">09-discussion.md</a></li>
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<h2>Examples</h2>
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<li><a href="../examples/seesubst.lua.html">seesubst.lua</a></li>
<li><a href="../examples/sipscan.lua.html">sipscan.lua</a></li>
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<li><a href="../examples/test-cmp.lua.html">test-cmp.lua</a></li>
<li><a href="../examples/test-data.lua.html">test-data.lua</a></li>
<li><a href="../examples/test-listcallbacks.lua.html">test-listcallbacks.lua</a></li>
<li><a href="../examples/test-pretty.lua.html">test-pretty.lua</a></li>
<li><a href="../examples/test-symbols.lua.html">test-symbols.lua</a></li>
<li><a href="../examples/testapp.lua.html">testapp.lua</a></li>
<li><a href="../examples/testclone.lua.html">testclone.lua</a></li>
<li><a href="../examples/testconfig.lua.html">testconfig.lua</a></li>
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<li><a href="../examples/testinputfields.lua.html">testinputfields.lua</a></li>
<li><a href="../examples/testinputfields2.lua.html">testinputfields2.lua</a></li>
<li><a href="../examples/testxml.lua.html">testxml.lua</a></li>
<li><a href="../examples/which.lua.html">which.lua</a></li>
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<h1>Module <code>pl.data</code></h1>
<p>Reading and querying simple tabular data.</p>
<p>
<pre><code>data.read 'test.txt'
==> {{10,20},{2,5},{40,50},fieldnames={'x','y'},delim=','}
</code></pre>
<p> Provides a way of creating basic SQL-like queries.</p>
<pre><code>require 'pl'
local d = data.read('xyz.txt')
local q = d:select('x,y,z where x > 3 and z < 2 sort by y')
for x,y,z in q do
print(x,y,z)
end
</code></pre>
<p> See <a href="../topics/06-data.md.html#Reading_Columnar_Data">the Guide</a></p>
<p> Dependencies: <a href="../modules/pl.utils.html#">pl.utils</a> , <a href="../modules/pl.array2d.html#">pl.array2d</a> (fallback methods)</p>
</p>
<h2><a href="#Functions">Functions</a></h2>
<table class="function_list">
<tr>
<td class="name" nowrap><a href="#Data.column_by_name">Data.column_by_name (name)</a></td>
<td class="summary">return a particular column as a list of values (method).</td>
</tr>
<tr>
<td class="name" nowrap><a href="#Data.select">Data.select (condn)</a></td>
<td class="summary">return a query iterator on this data (method).</td>
</tr>
<tr>
<td class="name" nowrap><a href="#Data.select_row">Data.select_row (condn)</a></td>
<td class="summary">return a row iterator on this data (method).</td>
</tr>
<tr>
<td class="name" nowrap><a href="#Data.copy_select">Data.copy_select (condn)</a></td>
<td class="summary">return a new data object based on this query (method).</td>
</tr>
<tr>
<td class="name" nowrap><a href="#Data.column_names">Data.column_names ()</a></td>
<td class="summary">return the field names of this data object (method).</td>
</tr>
<tr>
<td class="name" nowrap><a href="#Data.write_row">Data.write_row (f)</a></td>
<td class="summary">write out a row (method).</td>
</tr>
<tr>
<td class="name" nowrap><a href="#Data.write">Data.write (f)</a></td>
<td class="summary">write data out to file (method).</td>
</tr>
<tr>
<td class="name" nowrap><a href="#read">read (file, cnfg)</a></td>
<td class="summary">read a delimited file in a Lua table.</td>
</tr>
<tr>
<td class="name" nowrap><a href="#write">write (data, file, fieldnames, delim)</a></td>
<td class="summary">write 2D data to a file.</td>
</tr>
<tr>
<td class="name" nowrap><a href="#new">new (d, fieldnames)</a></td>
<td class="summary">create a new dataset from a table of rows.</td>
</tr>
<tr>
<td class="name" nowrap><a href="#query">query (data, condn, context, return_row)</a></td>
<td class="summary">create a query iterator from a select string.</td>
</tr>
<tr>
<td class="name" nowrap><a href="#filter">filter (Q, infile, outfile, dont_fail)</a></td>
<td class="summary">Filter input using a query.</td>
</tr>
</table>
<br/>
<br/>
<h2><a name="Functions"></a>Functions</h2>
<dl class="function">
<dt>
<a name = "Data.column_by_name"></a>
<strong>Data.column_by_name (name)</strong>
</dt>
<dd>
return a particular column as a list of values (method).
<h3>Parameters:</h3>
<ul>
<li><span class="parameter">name</span>
either name of column, or numerical index.</li>
</ul>
</dd>
<dt>
<a name = "Data.select"></a>
<strong>Data.select (condn)</strong>
</dt>
<dd>
return a query iterator on this data (method).
<h3>Parameters:</h3>
<ul>
<li><span class="parameter">condn</span>
the query expression</li>
</ul>
<h3>see also:</h3>
<ul>
<a href="../modules/pl.data.html#query">data.query</a>
</ul>
</dd>
<dt>
<a name = "Data.select_row"></a>
<strong>Data.select_row (condn)</strong>
</dt>
<dd>
return a row iterator on this data (method).
<h3>Parameters:</h3>
<ul>
<li><span class="parameter">condn</span>
the query expression</li>
</ul>
</dd>
<dt>
<a name = "Data.copy_select"></a>
<strong>Data.copy_select (condn)</strong>
</dt>
<dd>
return a new data object based on this query (method).
<h3>Parameters:</h3>
<ul>
<li><span class="parameter">condn</span>
the query expression</li>
</ul>
</dd>
<dt>
<a name = "Data.column_names"></a>
<strong>Data.column_names ()</strong>
</dt>
<dd>
return the field names of this data object (method).
</dd>
<dt>
<a name = "Data.write_row"></a>
<strong>Data.write_row (f)</strong>
</dt>
<dd>
write out a row (method).
<h3>Parameters:</h3>
<ul>
<li><span class="parameter">f</span>
file-like object</li>
</ul>
</dd>
<dt>
<a name = "Data.write"></a>
<strong>Data.write (f)</strong>
</dt>
<dd>
write data out to file (method).
<h3>Parameters:</h3>
<ul>
<li><span class="parameter">f</span>
file-like object</li>
</ul>
</dd>
<dt>
<a name = "read"></a>
<strong>read (file, cnfg)</strong>
</dt>
<dd>
read a delimited file in a Lua table.
By default, attempts to treat first line as separated list of fieldnames.
specify <code>no_convert</code> (default is to conversion), <code>numfields</code> (indices of columns known
to be numbers) and <code>thousands_dot</code> (thousands separator in Excel CSV is '.').
If <code>csv</code> is set then fields may be double-quoted and contain commas;
or a conversion error
<h3>Parameters:</h3>
<ul>
<li><span class="parameter">file</span>
a filename or a file-like object (default stdin)</li>
<li><span class="parameter">cnfg</span>
options table: can override <code>delim</code> (a string pattern), <code>fieldnames</code> (a list),</li>
</ul>
<h3>Returns:</h3>
<ol>
<li>
<a href="../modules/pl.data.html#pl.data">data</a> object, or <code>nil</code></li>
<li>
error message. May be a file error, 'not a file-like object'</li>
</ol>
</dd>
<dt>
<a name = "write"></a>
<strong>write (data, file, fieldnames, delim)</strong>
</dt>
<dd>
write 2D data to a file.
Does not assume that the data has actually been
generated with <a href="../modules/pl.data.html#new">new</a> or <a href="../modules/pl.data.html#read">read</a> .
<h3>Parameters:</h3>
<ul>
<li><span class="parameter">data</span>
2D array</li>
<li><span class="parameter">file</span>
filename or file-like object</li>
<li><span class="parameter">fieldnames</span>
list of fields (optional)</li>
<li><span class="parameter">delim</span>
delimiter (default tab)</li>
</ul>
</dd>
<dt>
<a name = "new"></a>
<strong>new (d, fieldnames)</strong>
</dt>
<dd>
create a new dataset from a table of rows.
Can specify the fieldnames, else the table must have a field called
'fieldnames', which is either a string of delimiter-separated names,
or a table of names. <br>
If the table does not have a field called 'delim', then an attempt will be
made to guess it from the fieldnames string, defaults otherwise to tab.
<h3>Parameters:</h3>
<ul>
<li><span class="parameter">d</span>
the table.</li>
<li><span class="parameter">fieldnames</span>
optional fieldnames</li>
</ul>
<h3>Returns:</h3>
<ol>
the table.
</ol>
</dd>
<dt>
<a name = "query"></a>
<strong>query (data, condn, context, return_row)</strong>
</dt>
<dd>
create a query iterator from a select string.
Select string has this format: <br>
FIELDLIST [ where LUA-CONDN [ sort by FIELD] ]<br>
FIELDLIST is a comma-separated list of valid fields, or '*'. <br> <br>
The condition can also be a table, with fields 'fields' (comma-sep string or
table), 'sort_by' (string) and 'where' (Lua expression string or function)
<h3>Parameters:</h3>
<ul>
<li><span class="parameter">data</span>
table produced by read</li>
<li><span class="parameter">condn</span>
select string or table</li>
<li><span class="parameter">context</span>
a list of tables to be searched when resolving functions</li>
<li><span class="parameter">return_row</span>
if true, wrap the results in a row table</li>
</ul>
<h3>Returns:</h3>
<ol>
<li>
an iterator over the specified fields, or nil</li>
<li>
an error message</li>
</ol>
</dd>
<dt>
<a name = "filter"></a>
<strong>filter (Q, infile, outfile, dont_fail)</strong>
</dt>
<dd>
Filter input using a query.
<h3>Parameters:</h3>
<ul>
<li><span class="parameter">Q</span>
a query string</li>
<li><span class="parameter">infile</span>
filename or file-like object</li>
<li><span class="parameter">outfile</span>
filename or file-like object</li>
<li><span class="parameter">dont_fail</span>
true if you want to return an error, not just fail</li>
</ul>
</dd>
</dl>
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