How facet resolves multiple records for the facetted parameter not documented #27
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Please let me know if there is a forum specifically for Altair questions and help and I will move this there.
I haven't been able to find in the documentation how facet resolves multiple entries for the facetted parameter.
In the MWE below, what does facet() do when it encounters 3 entries where P = HD, and T = 0, yet only plots one value at HD, 0 in the t_facet (T) plot.
Is this just a flawed plot?
MWE
import pandas as pd
import altair as alt
data = [{"P": "HD", "T": 0, "C":100, "Max": 1},
{"P": "HD", "T": 0, "C":400, "Max": 3},
{"P": "HD", "T": 0, "C":800, "Max": 0},
{"P": "HD", "T": 23, "C":100, "Max": 2},
{"P": "HD", "T": 23, "C":400, "Max": 1},
{"P": "HD", "T": 23, "C":800, "Max": 1},
{"P": "HD", "T": 80, "C":100, "Max": 7},
{"P": "HD", "T": 80, "C":400, "Max": 2},
{"P": "HD", "T": 80, "C":800, "Max": 1},
{"P": "LD", "T": 0, "C":100, "Max": 1},
{"P": "LD", "T": 0, "C":400, "Max": 2},
{"P": "LD", "T": 0, "C":800, "Max": 7},
{"P": "LD", "T": 23, "C":100, "Max": 7},
{"P": "LD", "T": 23, "C":400, "Max": 1},
{"P": "LD", "T": 23, "C":800, "Max": 0},
{"P": "LD", "T": 80, "C":100, "Max": 2},
{"P": "LD", "T": 80, "C":400, "Max": 0},
{"P": "LD", "T": 80, "C":800, "Max": 1}]
df = pd.DataFrame(data)
chart = alt.Chart(df).mark_bar().encode(x="P:N", y="Max:Q", color="P:N")
t_facet = chart.facet("T:N")
c_facet = chart.facet("C:N") P T C Max
0 HD 0 100 1
1 HD 0 400 3
2 HD 0 800 0
3 HD 23 100 2
4 HD 23 400 1
5 HD 23 800 1
6 HD 80 100 7
7 HD 80 400 2
8 HD 80 800 1
9 LD 0 100 1
10 LD 0 400 2
11 LD 0 800 7
12 LD 23 100 7
13 LD 23 400 1
14 LD 23 800 0
15 LD 80 100 2
16 LD 80 400 0
17 LD 80 800 1
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