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plotting a column name with '.' in it eventually leads to a vega error

See original GitHub issue

I’m doing an Altair chart with a color given by color=Color('gpuinfo.name:N', .... This produces an eventual Vega error.

(Why do I have a column with a period in its name? Reading nested JSONs into pandas is nicely handled by json_normalize, which flattens nested JSON levels into dot-separated column names.)

undefined:3
return x["gpuinfo"]["name"];
                   ^

TypeError: Cannot read property 'name' of undefined
    at Object.eval [as get] (eval at <anonymous> (/Users/jowens/Documents/working/vega/node_modules/datalib/src/util.js:147:20), <anonymous>:3:20)
    at Facetor.proto._cellkey (/Users/jowens/Documents/working/vega/node_modules/datalib/src/aggregate/aggregator.js:106:23)
    at Facetor.proto._cell (/Users/jowens/Documents/working/vega/node_modules/datalib/src/aggregate/aggregator.js:114:38)
    at Facetor.proto._add (/Users/jowens/Documents/working/vega/node_modules/datalib/src/aggregate/aggregator.js:151:19)
    at add (/Users/jowens/Documents/working/vega/src/transforms/Aggregate.js:174:31)
    at Array.forEach (native)
    at Aggregate.prototype.transform (/Users/jowens/Documents/working/vega/src/transforms/Aggregate.js:190:13)
    at Aggregate.prototype.evaluate (/Users/jowens/Documents/working/vega/src/transforms/Transform.js:48:15)
    at Node.dataRef (/Users/jowens/Documents/working/vega/src/scene/Scale.js:387:15)
    at Node.ordinal (/Users/jowens/Documents/working/vega/src/scene/Scale.js:127:20)

Issue Analytics

State:
Created 7 years ago
Comments:11 (6 by maintainers)

Top GitHub Comments

1reaction

jakevdpcommented, Feb 7, 2019

This is expected: x.x is one way Vega-Lite uses to refer to hierarchical data. If you want to use special characters in field names, they should be escaped. e.g.

alt.Chart(df).mark_line().encode(x=r"x\.x:Q", y="x\.x:Q")

This is true regardless of the Altair/Vega-Lite version you are using.

For more information, see field under Encoding Channel Options

0reactions

jakevdpcommented, Feb 7, 2019

Great, glad you got it working.

Regarding auto-escaping, there’s no functionality built-in for that… it would be a useful feature to have.

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