How to dissolve the dataset on multiple conditions - R

Question

Consider dataset the following dataset:

ID	Start time	End time	Traffic	Lane
1	01-01-2015	01-02-2015	500	1
1	01-01-2015	01-02-2015	400	2
1	01-02-2015	01-03-2015	250	1
1	01-02-2015	01-03-2015	250	2
2	01-01-2015	01-02-2015	80	1
2	01-02-2015	01-03-2015	70	1

I want to aggregate the traffic values based on multiple conditions. The traffic values should be aggregated based on a similar ID and Start time so that the output dataset becomes:

ID	Start time	End time	Traffic
1	01-01-2015	01-02-2015	900
1	01-02-2015	01-03-2015	500
2	01-01-2015	01-02-2015	80
2	01-02-2015	01-03-2015	70

What is a convenient way of achieving this?

Answer 1

You should achieve this by grouping group_by() and then summarize accordingly, e.g.

library(dplyr)    
df %>% 
      group_by(ID, start_time, End_time) %>% 
      summarise(Traffic = sum(Traffic))