Create LineString for unique values in Pandas DataFrame

问题

I have a pandas dataframe I would like to iterate over. For instance a simplified version of my dataframe can be:

abc    begin   end    ID     Lat      Long
def1    001    123    CAT    13.167   52.411
def2    002    129    DOG    13.685   52.532
def3    003    145    MOOSE  13.698   52.131
def1    004    355    CAT    13.220   52.064
def2    005    361    CAT    13.304   52.121
def3    006    399    DOG    12.020   52.277
def1    007    411    MOOSE  13.699   52.549
def2    008    470    MOOSE  11.011   52.723

I would like to iterate over each unique ID and create a (shapely)LineString from the matching Lat / Long columns.

grp = df.groupby('ID')
for x in grp.groups.items():
# this is where I need the most help

For the above example I would like to get three iterations with 3 LineStrings put back into a single dictionary.

{'CAT':LINESTRING (13.167 52.411, 13.22 52.064, 13.304 52.121), 'DOG':LINESTRING (13.685 52.532, 12.02 52.277), 'MOOSE':LINESTRING (13.698 52.131, 12.699 52.549, 13.011 52.723)}

回答1:

I don't have the LINESTRING package installed, but I guess you can easily convert what's in d into the format you need.

d = {}
df.groupby('ID').apply(lambda x: d.update({x.ID.iloc[0]:x[['Lat','Long']].values.tolist()}))

{'CAT': [[13.167, 52.411], [13.22, 52.064], [13.304, 52.121]],
 'DOG': [[13.685, 52.532], [12.02, 52.277]],
 'MOOSE': [[13.698, 52.131], [13.699, 52.549], [11.011, 52.723]]}

来源：https://stackoverflow.com/questions/44181883/create-linestring-for-unique-values-in-pandas-dataframe