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Given the following text description, write Python code to implement the functionality described below step by step
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Description:
 This notebook plots the number of origins of viviparity and reversions to oviparity, broken down by tree. The result is a grouped histogram.
Step1:  Read data using pandas.
Step2:  Pivot the table to group the data by tree.
Step3:  Plot using native pandas plotting.
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Python Code:
import pandas as pd
from pandas import *
import matplotlib.pyplot as plt
%matplotlib inline
from ggplot import *
from numpy import random 
plt.style.use('ggplot')
Explanation: This notebook plots the number of origins of viviparity and reversions to oviparity, broken down by tree. The result is a grouped histogram.
End of explanation
data = pd.read_csv("../Data/Histogram/pared_down.csv")
data
data.columns
Explanation: Read data using pandas.
End of explanation
table = pivot_table(data, index=['Tree'], columns=['Parameter'])
table
Explanation: Pivot the table to group the data by tree.
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table.plot(kind='bar', width=.7, sort_columns=True).set_ylim(0,75)
plt.tight_layout()
plt.savefig('exTotal.svg', bbox_inches='tight', dpi=300)
Explanation: Plot using native pandas plotting.
End of explanation
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