I have a data frame as shown below. How can I replace the NA? Looks like for the same device, source and timestamp the lat and long are same as well. So, the NA values should be: aaa, US, 33.23, -117.31 for the 2nd row. Am I thinking the right way? If not, then what is the best way to replace those missing values and in a correct way?
city country lat long timestamp source device
aaa US 33.23 -117.31 2015-04-12 11:51:16 ad-f w
<NA> <NA> NA NA 2015-04-12 11:51:16 ad-f w
bbb US 33.78 -117.96 2015-04-12 11:51:16 se-f m
bbb US 33.78 -117.96 2015-04-12 11:51:16 se-f m
aaa US 33.23 -117.31 2015-04-12 11:51:16 ad-f w
<NA> <NA> NA NA 2015-04-04 17:38:26 se-f m
<NA> <NA> NA NA 2015-04-04 17:38:26 ad-g m
ddd US 33.99 -118.09 2015-04-04 17:38:26 ad-g m
eee US 40.67 -73.94 2015-04-04 17:38:26 se-f m
<NA> <NA> NA NA 2015-03-02 00:04:12 ad-g w
Thanks in advance.