对于循环错误，SettingWithCopyWarning：正在尝试在 DataFrame 中的切片副本上设置值

Question

I tried to count spots that are in 100meter radius with GPS coordinates. My data has 4 columns like below;

Index     Longitude    Latitude      Count
1         35.897654    26.568987       0
2         32.98717     23.897740       0
3         36.23245     34.243246       0
.          ....         ....          ....
.          ....         ....          ....

I calculated distance from coordinates with Haversine method. I described it as a function.

haversine([x1,y1],[x2,y2]) gives the meter between GPS coordinates.

My problem occurs in below code;

for x in range(0,25486):
    for y in range(1,25486):
        a = haversine([cr.iloc[x][0],cr.iloc[x][1]],[cr.iloc[y][0],cr.iloc[y][1]])
        if a <= 100 and a > 0:
            cr.iloc[x][2]=cr.iloc[x][2]+1

it raises this error;

main :5: SettingWithCopyWarning: A value is trying to be set on a copy of a slice from a DataFrame

See the caveats in the documentation: http://pandas.pydata.org/pandas-docs/stable/indexing.html#indexing-view-versus-copy

I checked the document but I couldn't find something useful or I didn't understand it.

What I am doing wrong? What's the proper way to do this nested loop operation?

Thanks in advance.

Answer 1

cr.iloc[x][2]=cr.iloc[x][2]+1

this code doesn't set the value in dataframe

I've changed to;

for x in range(0,25486):
    t=0
    for y in range(0,25486):
        a = haversine([cr.iloc[x][1],cr.iloc[x][2]],[cr.iloc[y][1],cr.iloc[y][2]])
        if a <= 400 and a > 0:
            t = t+1   
    cr.set_value(x,'Adet',t)

Answer 2

By looking at your question, I didn't get an answer but my research to use .set_value lead me to something very similar.

I'm using .at[index, 'column'] = value

My code :

for index, row in customersOnMap.iterrows():
x = row.loc['customer_zip_code_prefix']
if x in list_zip_code.geolocation_zip_code_prefix.values:
    lat = list_zip_code[list_zip_code.geolocation_zip_code_prefix == x].geolocation_lat.values[0]
    long = list_zip_code[list_zip_code.geolocation_zip_code_prefix == x].geolocation_lng.values[0]
    customersOnMap.at[index, 'geolocation_lat'] = lat
    customersOnMap.at[index, 'geolocation_lng'] = long
else:
    print('Couldn t find the zip code', x, 'in the list.')

Link to further information :

https://www.dataindependent.com/pandas/pandas-set-values/