CODEWITHSUNDEEP
pythonpandas
Monica
Monica

Reputation: 1070

Sorting Dataframe according to two columns

I got the following DataFrame:

       R         System    Name
0      0.78       1        Methane - PAH
1      1.00       1        Methane - PAH
2      1.20       1        Methane - PAH
3      1.40       1        Methane - PAH
4      0.90       1        Methane - PAH
5      2.16       1        Methane - PAH
6      1.62       1        Methane - NT
7      1.35       1        Methane - NT
8      1.19       2        Methane - NT
9      1.14       2        Methane - NT
10     0.80       2        Methane - NT
11     1.03       2        Methane - PAH
12     0.89       2        Methane - PAH
13     0.92       2        Methane - PAH
14     1.08       2        Methane - PAH
15     0.86       2        Methane - PAH
16     0.84       2        Methane - PAH
17     0.95       3        Methane - PAH
19     0.97       3        Methane - PAH
20     1.00       3        Methane - NT
21     0.92       3        Methane - NT
22     0.80       3        Methane - PAH
23     0.90       3        Methane - PAH
24     1.00       3        Methane - PAH
25     1.20       3        Methane - NT
26     0.87       3        Methane - NT
27     1.40       3        Methane - PAH
28     0.89       3        Methane - PAH

I want to sort the Frame according to R but around a particular System :

       R         System   Name
0      0.78       1        Methane - PAH
1      0.90       1        Methane - PAH
2      1.00       1        Methane - PAH
3      1.20       1        Methane - PAH
4      1.35       1        Methane - NT
5      1.40       1        Methane - PAH
6      1.62       1        Methane - NT
7      0.80       2        Methane - NT
8      0.89       2        Methane - PAH
9      0.92       2        Methane - PAH
10     1.03       2        Methane - PAH
11     1.08       2        Methane - PAH
12     1.14       2        Methane - NT
13     1.19       2        Methane - NT
...
18     0.80       3        Methane - PAH
19     0.87       3        Methane - NT
20     0.90       3        Methane - PAH
21     0.92       3        Methane - NT
22     0.95       3        Methane - PAH
23     0.97       3        Methane - PAH
24     1.00       3        Methane - NT
25     1.00       3        Methane - PAH
26     1.20       3        Methane - NT
28     1.40       3        Methane - PAH

I know how to sort DataFrame by a column: df = df.sort_values(by = ['R'], ascending=True)

However I do not know how to do a 'partial sort'. I will be grateful for any hints.

Upvotes: 0

Views: 334

Answers (1)

grey_ranger
grey_ranger

Reputation: 1030

Since version 17.0, pandas has supported sorting by multiple column names. The documentation for the sort_values() function shows that you can pass a list to the by= keyword. The function will return a dataframe sorted by the first column in the list. Then within all matching values in the first column, the dataframe will be sorted by the second column, and so on.

The function call to sort your dataframe would be df = df.sort_values(by = ['System', 'R'], ascending=True).

Upvotes: 1

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