Searching for duplicate row entries (with different values!) and adding them up

Question

I have a Dataframe with 3 column entries in R. Number, Color, Quantity. I want to check my dataframe for rows that match their number and color, (Quantities may differ!). These rows need to be combined to one row with summed up quantities. An example table is:

Number	Color	Quantity
3475b	Black	2
4349	White	4
970c00	Yellow	1
3475b	Black	7
3641	Red	8
4349	Red	3

To sum it up: row 1 and 4 should be added up to a total quantity of 9. Row 2 and 6 have the same number but different color, so they stay apart. In this case the resulting table should have only 5 rows like:

Number	Color	Quantity
3475b	Black	9
4349	White	4
970c00	Yellow	1
3641	Red	8
4349	Red	3

Answer 1

In base R, we can use aggregate

aggregate(Quantity ~ ., df1, sum)

-output

#   Number  Color Quantity
#1  3475b  Black        9
#2   3641    Red        8
#3   4349    Red        3
#4   4349  White        4
#5 970c00 Yellow        1

data

df1 <- structure(list(Number = c("3475b", "4349", "970c00", "3475b", 
"3641", "4349"), Color = c("Black", "White", "Yellow", "Black", 
"Red", "Red"), Quantity = c(2L, 4L, 1L, 7L, 8L, 3L)), class = "data.frame",
row.names = c(NA, 
-6L))