[PYTHON/PANDAS] merge 함수 : how/left_on/right_on 인자를 사용해 데이터 조인하기

■ merge 함수의 how/left_on/right_on 인자를 사용해 데이터를 조인하는 방법을 보여준다.

▶ main.py


import pandas as pd

airQualityParameterDataFrame = pd.read_csv("air_quality_parameters.csv")

airQualityNO2DataFrame  = pd.read_csv("air_quality_no2_long.csv" , parse_dates = True)[["date.utc", "location", "parameter", "value"]]
AirQualityPM25DataFrame = pd.read_csv("air_quality_pm25_long.csv", parse_dates = True)[["date.utc", "location", "parameter", "value"]]

airQualityDataFrame = pd.concat([AirQualityPM25DataFrame, airQualityNO2DataFrame], axis = 0).sort_values("date.utc")

targetDataFrame = pd.merge(airQualityDataFrame, airQualityParameterDataFrame, how = "left", left_on = "parameter", right_on = "id")

print(targetDataFrame)

"""
                       date.utc            location parameter  value    id                                        description   name
0     2019-05-07 01:00:00+00:00  London Westminster       no2   23.0   no2                                   Nitrogen Dioxide    NO2
1     2019-05-07 01:00:00+00:00             FR04014       no2   25.0   no2                                   Nitrogen Dioxide    NO2
2     2019-05-07 01:00:00+00:00             BETR801      pm25   12.5  pm25  Particulate matter less than 2.5 micrometers i...  PM2.5
3     2019-05-07 01:00:00+00:00             BETR801       no2   50.5   no2                                   Nitrogen Dioxide    NO2
4     2019-05-07 01:00:00+00:00  London Westminster      pm25    8.0  pm25  Particulate matter less than 2.5 micrometers i...  PM2.5
...                         ...                 ...       ...    ...   ...                                                ...    ...
3173  2019-06-20 22:00:00+00:00             FR04014       no2   26.5   no2                                   Nitrogen Dioxide    NO2
3174  2019-06-20 23:00:00+00:00  London Westminster      pm25    7.0  pm25  Particulate matter less than 2.5 micrometers i...  PM2.5
3175  2019-06-20 23:00:00+00:00             FR04014       no2   21.8   no2                                   Nitrogen Dioxide    NO2
3176  2019-06-21 00:00:00+00:00  London Westminster      pm25    7.0  pm25  Particulate matter less than 2.5 micrometers i...  PM2.5
3177  2019-06-21 00:00:00+00:00             FR04014       no2   20.0   no2                                   Nitrogen Dioxide    NO2

[3178 rows x 7 columns]
"""

import pandas as pd

airQualityParameterDataFrame = pd.read_csv("air_quality_parameters.csv")

airQualityNO2DataFrame = pd.read_csv("air_quality_no2_long.csv" , parse_dates = True)[["date.utc", "location", "parameter", "value"]]

AirQualityPM25DataFrame = pd.read_csv("air_quality_pm25_long.csv", parse_dates = True)[["date.utc", "location", "parameter", "value"]]

airQualityDataFrame = pd.concat([AirQualityPM25DataFrame, airQualityNO2DataFrame], axis = 0).sort_values("date.utc")

targetDataFrame = pd.merge(airQualityDataFrame, airQualityParameterDataFrame, how = "left", left_on = "parameter", right_on = "id")

print(targetDataFrame)

"""

date.utc location parameter value id description name

0 2019-05-07 01:00:00+00:00 London Westminster no2 23.0 no2 Nitrogen Dioxide NO2

1 2019-05-07 01:00:00+00:00 FR04014 no2 25.0 no2 Nitrogen Dioxide NO2

2 2019-05-07 01:00:00+00:00 BETR801 pm25 12.5 pm25 Particulate matter less than 2.5 micrometers i... PM2.5

3 2019-05-07 01:00:00+00:00 BETR801 no2 50.5 no2 Nitrogen Dioxide NO2

4 2019-05-07 01:00:00+00:00 London Westminster pm25 8.0 pm25 Particulate matter less than 2.5 micrometers i... PM2.5

... ... ... ... ... ... ... ...

3173 2019-06-20 22:00:00+00:00 FR04014 no2 26.5 no2 Nitrogen Dioxide NO2

3174 2019-06-20 23:00:00+00:00 London Westminster pm25 7.0 pm25 Particulate matter less than 2.5 micrometers i... PM2.5

3175 2019-06-20 23:00:00+00:00 FR04014 no2 21.8 no2 Nitrogen Dioxide NO2

3176 2019-06-21 00:00:00+00:00 London Westminster pm25 7.0 pm25 Particulate matter less than 2.5 micrometers i... PM2.5

3177 2019-06-21 00:00:00+00:00 FR04014 no2 20.0 no2 Nitrogen Dioxide NO2

[3178 rows x 7 columns]

"""

▶ requirements.txt


numpy==2.1.2
pandas==2.2.3
python-dateutil==2.9.0.post0
pytz==2024.2
six==1.16.0
tzdata==2024.2

numpy==2.1.2

pandas==2.2.3

python-dateutil==2.9.0.post0

pytz==2024.2

six==1.16.0

tzdata==2024.2

※ pip install pandas 명령을 실행했다.

air_quality_parameters.csv
air_quality_no2_long.csv
air_quality_pm25_long.csv