Simple data analysis with Pandas - how to remove repetitive code - pandas

Question

Here's an example:
import pandas as pd
import matplotlib.pyplot as plt
import seaborn as sns
import matplotlib.dates as mdates
import matplotlib.ticker as ticker
import numpy as np
dfboth = {
'I': [1,2,3,4,5,6],
'S': ['X', 'Y', 'X', 'Y', 'X', 'Y'],
'DVAR': [800, 300, 820, 330, 910, 350],
'CVAR': [1001, 612, 990, 639, 600, 130]}
dfboth = pd.DataFrame(dfboth)
dfboth = dfboth.assign(DVARCHANGE=dfboth['DVAR'].diff(2))
dfboth = dfboth.assign(CVARCHANGE=dfboth['CVAR'].diff(2))
plt.rcParams["figure.figsize"] = (24, 9) # (w, h)
plt.subplot(2,2,1)
plt.plot('I','DVAR', data=dfboth[dfboth.S=="X"])
plt.plot('I','DVARCHANGE', data=dfboth[dfboth.S=="X"])
plt.title("X-D")
plt.legend()
plt.subplot(2,2,2)
plt.plot('I','DVAR', data=dfboth[dfboth.S=="Y"])
plt.plot('I','DVARCHANGE', data=dfboth[dfboth.S=="Y"])
plt.title("Y-D")
plt.legend()
plt.subplot(2,2,3)
plt.plot('I','CVAR', data=dfboth[dfboth.S=="X"])
plt.plot('I','CVARCHANGE', data=dfboth[dfboth.S=="X"])
plt.title("X-C")
plt.legend()
plt.subplot(2,2,4)
plt.plot('I','CVAR', data=dfboth[dfboth.S=="Y"])
plt.plot('I','CVARCHANGE', data=dfboth[dfboth.S=="Y"])
plt.title("Y-C")
plt.legend()
I have a series of data points (a time series), I=1,2,3 ... and they each pertain to a certain 'S', in this example, X and Y. For each reading, we have two variables DVAR and CVAR. I am trying to make this graph
I compare for S X and Y, DVAR and it's change from the previous reading, and CVAR and it's change in previous reading.
You can also see annoying repetition. But I actually have 12 S's not just X and Y. And I have more variables.
I believe there's a much better way of doing this than I have written using either stacked indexes or some kind of pivot table. But I've not been able to figure it out!

Answer 1

You can use a for-loop:
plot_titles = ["X-D", "Y-D", "X-C", "Y-C"]
y1 = ['DVAR', 'DVAR', 'CVAR', 'CVAR']
y2 = [y + 'CHANGE' for y in y1]
data1 = ["X", "Y", "X", "Y"]
for i in range(4):
plt.subplot(2, 2, i+1)
plt.plot('I', y1[i], data = dfboth[dfboth.S == data1[i]])
plt.plot('I', y2[i], data = dfboth[dfboth.S == data1[i]])
plt.title(plot_titles[i])
plt.legend()