R - How to sum all values based on both a certain date AND string?

Question

I'm currently working with a data frame where I wish to summarize drug dosage per day per patient. With the tidyverse I tried using a

df%>%
group_by (patient, date)%>%
summarise(doseperday = aggregate(drugdose)

but no luck.

I.e.

|patient|drugdose|date    |
|Bob    |5       |10/10/18|
|Bob    |3       |10/10/18|
|Bob    |4       |10/11/18|
|Bob    |1       |10/11/18|
|Jim    |5       |10/10/18|
|Jim    |8       |10/10/18|
|Jim    |3       |10/11/18|
|Jim    |1       |10/11/18|

I want to get the following:

|patient|drugdose|date    |
|Bob    |8       |10/10/18|
|Bob    |5       |10/11/18|
|Jim    |12      |10/10/18|
|Jim    |4       |10/11/18|

Thanks for the help.