How to avoid overlapping texts in Altair plots in Python

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import altair as alt
import pandas as pd

# assign data of lists.  
ProxyData = {'Separation Mechanism': ['Force1', 'Force2', 'Force3', 'Force4', 'Force5', 
'Force6' ], 'Parm1':[1,100,2.5,38,20,30], 'Parm2':[300,1000,150,1500,1000,1300], 'Parm3': 
[0.1,30,7.5,1,30,270],'Parm4':[81650,9000,2000,4000,2000,1540] }  

# Create DataFrame  
df3 = pd.DataFrame(ProxyData)  

 base =alt.Chart(df3).mark_bar(opacity=0.5).encode(
  alt.X('Parm1', scale=alt.Scale(type='log'), axis = alt.Axis(title='Particle')),
  x2='Parm2',
  y=alt.Y('Parm4',sort = None, scale=alt.Scale(type='log'), axis = alt.Axis(title='Rate')),
  y2 = 'Parm3'
  ).properties(width = 500, height = 400
  )
  bars = base.mark_bar(opacity=0.5).encode(
   color= alt.Color('Separation Mechanism', scale=alt.Scale(scheme='accent'))
  )

text = base.mark_text(
align='right',
baseline='middle',
color='black',
dx=100, dy =3, fontSize = 14).encode(text='Separation Mechanism')
bars+text

The link here describes the label transformation in javascript but I want adapt it for python Online Altair documentation on label transformation I have tried to include .transform(avoidMarks = ["Force5", "Force6"]) to "text" section but it shows error as undefined object not callable. I request you to kindly help me on how to use lable transform to avoid the overlapping text. Thank you very much.

vega-lite altair bar-chart label python
2 Answers

This was just added to VegaLite and won't be in Altair until the next release of Vega-Lite and Altair is upgraded to support the latest version of Vega-Lite.

user_21668230 
  {
    "config": {"view": {"continuousWidth": 400, "continuousHeight": 300}},
     "layer": [
   {
  "mark": {"type": "bar", "opacity": 0.5},
  "encoding": {
    "color": {
      "type": "nominal",
      "field": "Separation Mechanism",
      "scale": {"scheme": "accent"}
    },
    "x": {
      "type": "quantitative",
      "axis": {"title": "Particle"},
      "field": "Parm1",
      "scale": {"type": "log"}
    },
    "x2": {"field": "Parm2"},
    "y": {
      "type": "quantitative",
      "axis": {"title": "Rate"},
      "field": "Parm4",
      "scale": {"type": "log"},
      "sort": null
    },
    "y2": {"field": "Parm3"}
  },
  "height": 400,
  "width": 500
  },
  {
  "mark": {
    "type": "text",
    "align": "right",
    "baseline": "middle",
    "color": "black",
    "dx": 100,
    "dy": 3,
    "fontSize": 14
  },
  "encoding": {
    "text": {"type": "nominal", "field": "Separation Mechanism"},
    "x": {
      "type": "quantitative",
      "axis": {"title": "Particle"},
      "field": "Parm1",
      "scale": {"type": "log"}
    },
    "x2": {"field": "Parm2"},
    "y": {
      "type": "quantitative",
      "axis": {"title": "Rate"},
      "field": "Parm4",
      "scale": {"type": "log"},
      "sort": null
    },
    "y2": {"field": "Parm3"}
  },
  "height": 400,
  "width": 500
}
 ],
 "data": {"name": "data-4b7e34321793962372af06f754b1c5ca"},
 "$schema": "https://vega.github.io/schema/vega-lite/v4.8.1.json",
 "datasets": {
  "data-4b7e34321793962372af06f754b1c5ca": [
  {
    "Separation Mechanism": "Force1",
    "Parm1": 1,
    "Parm2": 300,
    "Parm3": 0.1,
    "Parm4": 81650
  },
  {
    "Separation Mechanism": "Force2",
    "Parm1": 100,
    "Parm2": 1000,
    "Parm3": 30,
    "Parm4": 9000
  },
  {
    "Separation Mechanism": "Force3",
    "Parm1": 2.5,
    "Parm2": 150,
    "Parm3": 7.5,
    "Parm4": 2000
  },
  {
    "Separation Mechanism": "Force4",
    "Parm1": 38,
    "Parm2": 1500,
    "Parm3": 1,
    "Parm4": 4000
  },
  {
    "Separation Mechanism": "Force5",
    "Parm1": 20,
    "Parm2": 1000,
    "Parm3": 30,
    "Parm4": 2000
  },
  {
    "Separation Mechanism": "Force6",
    "Parm1": 30,
    "Parm2": 1300,
    "Parm3": 270,
    "Parm4": 1540
  }
  ]
  }
  }




  Hi @joelostblom, thank you very much for your reply. How to add label transform function to get rid off overlapping labels.
user_34543530
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