Color= makes graph disappear

[Notenlish]

What happened?

my data.csv:

Temp_Range,Time,Gross_Final_Mass,Water_Final_Mass,Lost_Mass
40-45,30.1,1246,677,2
40-45 ,28.0,1246,677,2
40-45  ,28.63,1246,677,2
45-50,35.0,1246,677,2
45-50 ,25.0,1246,677,2
45-50  ,30.3,1246,677,2
50-55,29.4,1244,675,4
50-55 ,32.4,1245,676,3
50-55  ,29.2,1243,674,5
55-60,32.3,1242,673,6
55-60 ,32.0,1242,673,6
55-60  ,30.0,1243,674,5
60-65,34.4,1241,672,7
60-65 ,35.2,1241,672,7
60-65  ,29.0,1241,672,7

import polars
import altair as alt

df = polars.read_csv("data.csv")

chart = df.plot.line(
    x="Temp_Range",
    y=alt.Y("Gross_Final_Mass",
        scale=alt.Scale(domain=[1240, 1250])
    )
)

chart.save("gross final mass.png")

Basically, I have a few test results of me heating water in different temperature ranges and I want to create an graph out of it. I had to add a few spaces to the temp ranges otherwise it'd just accept them all as a single value, not multiple values. When I add color="Temp_Range" to there, the lines just disappear for some reason.

here's the output without color=:

here's the output with color=

What would you like to happen instead?

I want the same temperature ranges to have same color, but be colored differently than other temperature ranges(eg: 40-45 is orange, 45-50 is green etc.)

Which version of Altair are you using?

5.5.0

[dangotbanned]

@Notenlish

here's the output with color=

Could you provide the full code block for that please?

E.g. the exact difference from:

Code block

import polars
import altair as alt

df = polars.read_csv("data.csv")

chart = df.plot.line(
    x="Temp_Range",
    y=alt.Y("Gross_Final_Mass",
        scale=alt.Scale(domain=[1240, 1250])
    )
)

chart.save("gross final mass.png")

---

However I suspect the issue is related to the values in "Temp_Range" itself.

It looks like trailing spaces were added at the source for duplicate "Temp_Range"(s).

 Temp_Range,Time,Gross_Final_Mass,Water_Final_Mass,Lost_Mass
 40-45,30.1,1246,677,2
-40-45 ,28.0,1246,677,2
-40-45  ,28.63,1246,677,2
+40-45,28.0,1246,677,2
+40-45,28.63,1246,677,2
 45-50,35.0,1246,677,2
-45-50 ,25.0,1246,677,2
-45-50  ,30.3,1246,677,2
+45-50,25.0,1246,677,2
+45-50,30.3,1246,677,2
 50-55,29.4,1244,675,4
-50-55 ,32.4,1245,676,3
-50-55  ,29.2,1243,674,5
+50-55,32.4,1245,676,3
+50-55,29.2,1243,674,5
 55-60,32.3,1242,673,6
-55-60 ,32.0,1242,673,6
-55-60  ,30.0,1243,674,5
+55-60,32.0,1242,673,6
+55-60,30.0,1243,674,5
 60-65,34.4,1241,672,7
-60-65 ,35.2,1241,672,7
-60-65  ,29.0,1241,672,7
+60-65,35.2,1241,672,7
+60-65,29.0,1241,672,7

You should be able to fix data.csv after reading like this:

import polars as pl

df = pl.read_csv("data.csv").with_columns(pl.col("Temp_Range").str.strip_chars_end())

Whatever you're using to produce this data, is likely using this column as an index - but is compensating for non-unique values.
You might be able to prevent this at the source with an explicit index?

[FELLIX000]

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