Matplotlib pyplot set axis limits after rescaling equal

Question

I have something like the following dataframe where each record is a point along a line. Fields include distance from the line's beginning and point elevation.

>>> import pandas as pd
>>> import matplotlib.pyplot as plt
>>> 
>>> df=pd.DataFrame()
>>> df['Distance']=[5,100,200,300,350,370,400]
>>> df['Elevation']=[0,5,10,5,10,15,20]
>>> df
   Distance  Elevation
0         5          0
1       100          5
2       200         10
3       300          5
4       350         10
5       370         15
6       400         20
>>>

I want to create a plot that shows the elevation profile. Both distance and elevation are scaled in feet and I want it so increments of x and y have the same length (so the plot more realistically shows the elevation profile).

>>> plt.plot(df['Distance'],df['Elevation'])
[<matplotlib.lines.Line2D object at 0x0A1C7EB0>]
>>> plt.axis('equal')
(0.0, 400.0, 0.0, 20.0)
>>> plt.show()
>>>

Now that scaling is correct (a foot is represented by the same distance in both the x and y axis) how can I set the y limits so that they better suit the data (from -5 to 25 for example)?

tmdavison · Accepted Answer · 2015-12-10 21:07:57Z

2

If you use the OO approach, then you can use ax.set_ylim(-5,25):

import pandas as pd
import matplotlib.pyplot as plt

df=pd.DataFrame()
df['Distance']=[5,100,200,300,350,370,400]
df['Elevation']=[0,5,10,5,10,15,20]

fig = plt.figure()
ax = fig.add_subplot(111, aspect='equal')
ax.plot(df['Distance'],df['Elevation'])
ax.set_ylim(-5,25)

answered Dec 10, 2015 at 21:07

tmdavison

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2 Comments

AJG519 Over a year ago

thank you that's great. what does "the OO approach" stand for?

tmdavison Over a year ago

object-orientated. I.e. making a figure and axes, and then calling ax.plot, ax.set_ylim, fig.savefig etc. rather than plt.plot, plt.ylim, etc.

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