Percentage change to plot in histogram

Question

I am trying to plot histogram of percentage change in stock my code looks like:

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
data = pd.read_csv("M:/Trading/1.JOZO/ALXN.csv")
dataframe = (data['Adj Close'])
zmena1 = (dataframe.pct_change(periods = 1)*100)
data["Zmena"] = zmena1
plt.hist(zmena1, bins = "auto", range = "auto" )
plt.show

but i get an error:

 mn, mx = [mi + 0.0 for mi in range]

TypeError: Can't convert 'float' object to str implicitly

I tried str(zmena1) but can to get it... Do not know how to move through this one...

Answer 1

From the name of the csv file, I can guess that your data can be retrieved from Yahoo finance, so using the Remote Access datareader I'm downloading all 2016 data to play with:

import datetime
data = web.DataReader('ALXN', data_source='yahoo', 
                      start=datetime.datetime(2016, 1, 1))

Now I can calculate the percent change in the [0,100] range

data['Zmena'] = data['Adj Close'].pct_change(periods=1)*100

From there, I would definitely use the built-in DataFrame.hist function:

data['Zmena'].hist()

---

Using plt.hist

In case you do want to use plt.hist instead, you need to filter out the NaN (not a number), in particular you will always have one as the first entry:

print(data[['Adj Close','Zmena']].head())

             Adj Close     Zmena
Date                            
2016-01-04  184.679993       NaN
2016-01-05  184.899994  0.119126
2016-01-06  184.070007 -0.448884
2016-01-07  174.369995 -5.269741
2016-01-08  168.130005 -3.578592

So, in order to use plt.hist:

plt.hist(data.Zmena.dropna())

Another problem is that you're specifying bins = "auto", range = "auto" , when really you should just not pass them if you want to default. See the documentation for both parameters at pyplot.hist