Reduce dataframe rows with filter by ID

Question

I have the following dataframe:

      import pandas as pd

      dataframe = pd.DataFrame({'ID_Sensor': [1, 1, 1, 2, 2, 3, 3], 
                      'Type': ['Analog', 'Analog', 'Analog', 'Dig', 'Dig', 'Analog', 'Analog'],
                      'Value': [100, 200, 300, 1, 0, 400, 500]})

I would like to keep only the first line of each of the sensor identifiers. I tried to use the head () function, but it only returns the first line:

      dataframe.head(1)

My output:

      ID_Sensor    Type     Value
            1     Analog     100

Desired output:

     ID_Sensor  Type    Value
        1       Analog  100
        2        Dig     1
        3       Analog  400

The lines are not duplicated. Evolve columns with different values. — Jane Borges, Mar 03 '20 at 21:39

score 1 · Accepted Answer · answered Mar 03 '20 at 21:33

1

Please use groupby and chain .first

dataframe.groupby(['ID_Sensor','Type'])['Value'].first()

answered Mar 03 '20 at 21:33

wwnde

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How do you return in dataframe format? – Jane Borges Mar 03 '20 at 21:38
If that's what you want, then use drop duplicates. Reference to the drop duplicate answers. – wwnde Mar 03 '20 at 21:43
1

You can method chain `.to_frame()` to @wwnde's solution. This will change the answer from a series object to a dataframe. – Wayne Lambert Mar 03 '20 at 21:47
1

I managed to solve using: df = dataframe.groupby('ID_Sensor', as_index = False)['Type', 'Value'].first() – Jane Borges Mar 03 '20 at 21:47

Reduce dataframe rows with filter by ID

1 Answers1