I have this Pandas data in which some values are missing. For example, in row 542 the value of LATITUDE is missing. My goal is based on the condition CNTY_CITY_LOC to fill the missing value of LATITUDE by applying if elif and apply function in Pandas. After I apply the if statement with the apply function of Pandas, the missing value is replaced but all other values in the LATITUDE column are missing. What am I doing wrong? Thanks for your help

Missing values in column LATITUDE row 542

IF statement apply function

Missing values in column Latitude

CodePudding user response：

First is necessary return value if no match, here NaN and for repalce only missing values in CA_LOCATION['LATITUDE'] use Series.fillna:

def CA_LATITUDE(county_CODE):
    if county_CODE == 4710:
       return 41.5188
    else:
       return np.nan

CA_LOCATION['LATITUDE'] = CA_LOCATION['LATITUDE'].fillna(CA_LOCATION.CNTY_CITY_LOC.apply(CA_LATITUDE))

Better is use Series.fillna with mapping by dictionary:

d= {4710:41.5188, 4711:41.5288...}
CA_LOCATION['LATITUDE'] = CA_LOCATION['LATITUDE'].fillna(CA_LOCATION.CNTY_CITY_LOC.map(d))