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Iteration 72: Add value_counts — count unique values in Series and DataFrame
- `valueCounts(series, opts)`: count or normalize unique values, with sort/ascending/dropna - `dataFrameValueCounts(df, opts)`: count unique row combinations across all or subset of columns - 25 unit + property-based tests (fast-check); all pass - Interactive playground page: playground/value_counts.html - Wire up elem_ops exports (clip/seriesAbs/seriesRound) to stats barrel and main index Run: https://github.com/githubnext/tsessebe/actions/runs/24010521196 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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‎playground/value_counts.html‎

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<!doctype html>
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<html lang="en">
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<head>
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<meta charset="UTF-8" />
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<meta name="viewport" content="width=device-width, initial-scale=1.0" />
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<title>tsb — value_counts</title>
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a { color: #2563eb; }
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<body>
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<h1>tsb — <code>value_counts</code></h1>
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<p>
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Count unique values in a <strong>Series</strong> or unique row combinations in a
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<strong>DataFrame</strong>. Mirrors
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<a href="https://pandas.pydata.org/docs/reference/api/pandas.Series.value_counts.html"
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><code>pandas.Series.value_counts()</code></a
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>
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and
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<a href="https://pandas.pydata.org/docs/reference/api/pandas.DataFrame.value_counts.html"
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><code>pandas.DataFrame.value_counts()</code></a
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>.
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</p>
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<h2>1 · Basic usage (Series)</h2>
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<pre><code>import { Series } from "tsb";
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import { valueCounts } from "tsb";
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const s = new Series({ data: ["apple", "banana", "apple", "cherry", "banana", "apple"] });
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const vc = valueCounts(s);
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// index → ["apple", "banana", "cherry"]
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// values → [3, 2, 1] (sorted descending by default)</code></pre>
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<div class="output">index → apple=3 banana=2 cherry=1</div>
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<h2>2 · Normalize — return proportions</h2>
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<pre><code>const pct = valueCounts(s, { normalize: true });
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// values → [0.5, 0.333…, 0.167…] (must sum to 1)</code></pre>
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<div class="output">apple=0.50 banana=0.33 cherry=0.17</div>
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<h2>3 · Sort order</h2>
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<pre><code>// Ascending order (least frequent first)
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const asc = valueCounts(s, { ascending: true });
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// Preserve insertion order (no sort)
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const ins = valueCounts(s, { sort: false });</code></pre>
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<h2>4 · Missing-value handling</h2>
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<pre><code>const sWithNull = new Series({ data: ["a", null, "b", null, "a"] });
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// dropna=true (default) — exclude nulls
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const dropNull = valueCounts(sWithNull);
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// index → ["a", "b"], values → [2, 1]
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// dropna=false — include nulls
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const keepNull = valueCounts(sWithNull, { dropna: false });
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// index → ["a", "b", null], values → [2, 1, 2]</code></pre>
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<div class="output">dropna=true : a=2 b=1
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dropna=false: a=2 b=1 null=2</div>
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<h2>5 · DataFrame value_counts</h2>
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<pre><code>import { DataFrame } from "tsb";
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import { dataFrameValueCounts } from "tsb";
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const df = DataFrame.fromRecords([
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{ city: "NYC", temp: "hot" },
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{ city: "NYC", temp: "cold" },
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{ city: "LA", temp: "hot" },
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{ city: "NYC", temp: "hot" },
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]);
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const vc = dataFrameValueCounts(df);
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// Counts each unique (city, temp) combination
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// "NYC|hot" → 2
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// "NYC|cold" → 1
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// "LA|hot" → 1</code></pre>
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<div class="output">NYC|hot=2 NYC|cold=1 LA|hot=1</div>
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<h2>6 · DataFrame subset</h2>
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<pre><code>// Restrict to a subset of columns
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const vc2 = dataFrameValueCounts(df, { subset: ["city"] });
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// Only counts by city: NYC=3, LA=1</code></pre>
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<div class="output">NYC=3 LA=1</div>
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<h2>7 · API reference</h2>
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<pre><code>// Series
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valueCounts(series, {
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normalize?: boolean, // default false — return proportions instead of counts
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sort?: boolean, // default true — sort by frequency
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ascending?: boolean, // default false — highest count first when sort=true
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dropna?: boolean, // default true — exclude missing values
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}): Series&lt;number&gt;
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// DataFrame
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dataFrameValueCounts(df, {
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subset?: readonly string[], // columns to use (default: all)
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normalize?: boolean,
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sort?: boolean,
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ascending?: boolean,
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dropna?: boolean,
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}): Series&lt;number&gt;</code></pre>
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<div class="note">
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<strong>Note:</strong> The result Series is indexed by the unique values (or composite
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<code>"v1|v2|…"</code> strings for DataFrames). Use <code>.index.values</code> and
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<code>.values</code> to inspect the labels and counts respectively.
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</div>
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<p>← <a href="index.html">Back to feature list</a></p>
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</body>
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</html>

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