Hi my gorgeous friend on the Internet, I have a question about how to plot a Chart in Altair.

I have been struggling with this error since yesterday and still haven't plotted successfully.

I first imported some modules and data,

import pandas as pd
import altair as alt
import numpy as np

url = "https://github.com/byuidatascience/data4missing/raw/master/data-raw/flights_missing/flights_missing.json"
flights = pd.read_json(url)
flights.head()

Then, I used groupby() to add all num_of_total_flights together for each airport_code.

ttl = flights.groupby('airport_code')['num_of_flights_total'].sum()
ttl

After I checked ttl was fine, I wanted to plot the chart.

alt.Chart(ttl).mark_bar().encode(
    y="airport_code",
    x="num_of_flights_total",
)

Then I got this error message: num_of_flights_total encoding field is specified without a type; the type cannot be automatically inferred because the data is not specified as a pandas.DataFrame.

Does anyone know how to solve this?? Thanks for your valuable time in advance.

CodePudding user response：

Hello there charismatic stranger, I have an answer to your question. The error message is misleading in this case (and will likely be