How to plot graph against index in python

Question

The data looks like this:

        1       2       3       4
foo             
t0      95      95.5    75.5    85
t1      95.75   95.5    75.5    85
t2      96.5    95.5    75.5    85
t3      96.5    95.5    75.5    85
t4      96.5    95.5    75.5    85
...     ...     ...    ...  ...
t9996   95.5    95      75.5    85.5
t9997   95.5    95      75.5    85.5
t9998   95.5    95      75.5    85.5
t9999   95.5    95      75.5    85.5
t10000  95.5    95      75.5    85.5

I want to plot the 4 time series against the index. Using code:

df.plot(x = 'foo', y = '1')

I received this error:

KeyError: 'foo'

How should I do this?

score 3 · Answer 1 · answered Nov 22 '19 at 05:27

3

Use this. If x argument isn't provided, DataFrame.plot() takes df.index as default.

df.plot(y='1')

answered Nov 22 '19 at 05:27

Reuben

467
3
9

Hi @Reuben thank you for helping. I received `KeyError: '1'`. Do you know why? – nilsinelabore Nov 22 '19 at 23:49
@nilsinelabore You recieve the error if '1' is not a column name in the dataframe – Reuben Nov 23 '19 at 01:14

score 2 · Answer 2 · answered Nov 22 '19 at 05:07

2

You can use,

plt.plot(df.index,df['1'])

answered Nov 22 '19 at 05:07

Vinod Sawant

613
2
5
14

Hi @Vinod thanks for your answer. I received `KeyError: '1'`. Do you know why? – nilsinelabore Nov 22 '19 at 23:55
'1' is not the column name in your dataframe, Solution to this would be using iloc which does not take column by its name but by index as follows, plt.plot(df.index,df.iloc[:,1]) – Vinod Sawant Nov 23 '19 at 02:52

score 2 · Accepted Answer · answered Nov 22 '19 at 07:14

To add on to the discussion, I am going to demonstrate three plotting methods (from most straightforward to least) using the first five points of your data frame.

Import libraries

import pandas as pd
import matplotlib.pylab as plt

The sample dataframe

         1     2     3   4
foo                       
t0   95.00  95.5  75.5  85
t1   95.75  95.5  75.5  85
t2   96.50  95.5  75.5  85
t3   96.50  95.5  75.5  85
t4   96.50  95.5  75.5  85

Method 1

df.plot()
plt.show()

Method 2

df.reset_index().plot(x='foo')
plt.show()

Method 3

plt.plot(df.index,df)
plt.legend(df.columns)
plt.xlabel(df.index.name)
plt.show()

How to plot graph against index in python

3 Answers3

Method 1

Method 2

Method 3

Output (the same for all methods)