How to make operations on python dataframe based on specific values of another column?

问题

I am new to python data analysis. Following is an example dataset:

d2 = {'Index': [0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1], 'journey_time':[95.546,132.945,147.538,301.307,42.907,129.008,102.900,112.620,234.334,103.321,82.337,154.817,20.076,85.717,94.362,45.032],'edge':['s_b','c_d','b_d','c_e','d_f','s_a','a_c','d_c','c_e','a_c','d_c','s_a','d_f','s_b','b_d','c_d']}
df2=pd.DataFrame(data=d2)

I want to create a new data frame where there is one row for each index with new columns. The rules for the new columns are as such:

se1 = s_a + a_c + c_e
se2 = s_b + b_d + d_c + c_e
sf1 = s_b + b_d + d_f
sf2 = s_a + a_c + c_d + d_f

Also, I have further variations in my calculations such as

eq_time1 = (200/(s_a + a_c)) + c_e
eq_time2 = (200/(s_b + b_d + d_c)) + c_e

The values of the edges in the rules are the corresponding journey time for each unique index. I am not sure how to write this in python dataframe. Following is my expected output:

df3 = {'Index':[0,1],'se1':[129.008+102.900+301.307,154.817+103.321+234.334],'se2':[95.546+147.538+112.620+301.307,85.717+94.362+82.337+234.334],'sf1':[95.546+147.538+42.907,85.717+94.362+20.076],'sf2':[129.008+102.900+132.945+42.907,154.817+103.321+45.032+20.076 ],'eq_time1':[(200/(129.008+102.900))+301.307,(200/(154.817+103.321))+234.334   ], 'eq_time2' : [(200/(95.546+147.538+112.620))+301.307,(200/(85.717+94.362+82.337))+234.334]}

Please help!

回答1:

If you have just those 4 paths in your data, you can calculate the times in pandas as follows:

paths = {
  'se1': ['s_a', 'a_c', 'c_e'],
  'se2': ['s_b', 'b_d', 'd_c', 'c_e'],
  'sf1': ['s_b', 'b_d', 'd_f'],
  'sf2': ['s_a', 'a_c', 'c_d', 'd_f']
}

paths = {
  'se1': ['s_a', 'a_c', 'c_e'],
  'se2': ['s_b', 'b_d', 'd_c', 'c_e'],
  'sf1': ['s_b', 'b_d', 'd_f'],
  'sf2': ['s_a', 'a_c', 'c_d', 'd_f']
}

df3 = pd.DataFrame({'Index': df2['Index'].unique()}).set_index('Index')

for k, v in paths.items():
  df3[k] = df2[df2.edge.isin(v)].groupby('Index')['journey_time'].sum()
  last_edge_times = df2[df2.edge==v[-1]].set_index('Index')
  df3['eq_time_'+k] = 200.0/(df3[k] - last_edge_times.journey_time) + last_edge_times.journey_time

For any path p, eq_time_p column stores the eq_times as given by your equations.

来源：https://stackoverflow.com/questions/62242824/how-to-make-operations-on-python-dataframe-based-on-specific-values-of-another-c

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python

numpy

dataframe

data-analysis