Plot X vs. Y in Matplotlib, colored by third variable in Pandas data frame

Question

I have a sample data frame presented as ;

df=pd.DataFrame({'day': [1, 1, 2, 2, 3, 3, 4, 4],
                 'type': ['car', 'bike', 'car', 'bike', 'car', 'bike', 'car', 'bike'],
                 'percent': [21, 23, 56, 3, 15, 6, 7, 19]}

I need to make a line plot (Y=percent) vs. (X=day), we need two lines in the same plot colored by the variable type. Can we do it using Matplotlib? I tried the following code;

fig, ax =plt.subplots(figsize=(12,4))
plt.plot("day", "percent", color='type',data=df)
ax.set_title("Percentage of Deliveries")

ax.set_ylabel("Delivery Percent")

plt.show()

But I am getting an error;

Invalid RGBA argument: 'type'

Kindly help.

chris · Accepted Answer · 2020-06-30 22:36:07Z

1

If your third variable was not comprised of string categories, you could do

plt.scatter("day", "percent", c='type',data=df)

But this will error for your example because type column values are strings. What you're really looking to do is plot by a grouping (Scatter plots in Pandas/Pyplot: How to plot by category). You can group first then loop over the groups to plot:

grouped=df.groupby('type')
for name, group in grouped:
    plt.plot(group.day,group.percent)

answered Jun 30, 2020 at 22:36

chris

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2 Comments

jay Over a year ago

Appreciate your reply, actually I need to make a line plot, apologize if it was not clear.will the approach still be identical? kindly advice. In other words, I need to make 2 line plots in the same figure, of different colors

chris Over a year ago

When you loop over the groups, every time you call plt.plot() it will plot a new line with a new color.

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