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categorical histogram: the unique bar re-counts singletons already shown as top values

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
85/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
pandas, python
Domain
data-visualization

Research direction

Start in histogram.py at categorical_dict and follow how categorical_histogram separates the top values from the remainder; the issue includes a reproducer using pandas and notes that the shared function also serves polars. Verify that the unique count includes only singleton values outside the top values, and that the displayed bars no longer exceed 100% for the reproducer.

Written by the indexing model from the issue text.

Description

Histograms

Problem

categorical_dict (histogram.py:78) sets unique_count = sum(val_counts == 1) over every value, including the top 7 that categorical_histogram already draws one by one. When fewer than 7 values repeat, the singletons in the top 7 are counted twice and the bars add up to more than 100%. Sixteen rows with counts 5, 3 and eight singletons draw a 31, b 19, five singletons at 6 each, and unique 50, 130% in total. A one-row column reads 1.5 100 and unique 100. Pandas and polars share the function. #365 reported unique at 100% on a polars bool column.

import pandas as pd
from buckaroo.customizations.pd_stats_v2 import PD_ANALYSIS_V2
from buckaroo.pluggable_analysis_framework.stat_pipeline import StatPipeline

sd, _ = StatPipeline(PD_ANALYSIS_V2, unit_test=False).process_df(pd.DataFrame({"a": ["a"] * 5 + ["b"] * 3 + [f"s{i}" for i in range(8)]}))
print([(b["name"], b.get("cat_pop", b.get("unique"))) for b in sd["a"]["histogram"]])
# [('a', 31.0), ('b', 19.0), ('s0', 6.0), ('s1', 6.0), ('s2', 6.0), ('s3', 6.0), ('s4', 6.0), ('unique', 50.0)]

Suggested fix

Count only the singletons outside the top values (rest_vals == 1).

Context

Found while probing histogram edge cases after #1069. Reproduces on main at e88ace91.

Dominant language
Python
Stars
685
Forks
17
Avg merge
23h 34m
Merged PRs (30d)
24

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