汇总（和相乘）行中的行-R

Question

I am trying to sum (and multiply) all my rows in a table to the final output would be just one row and multiple columns.

My data looks like this:

##      Typ-1 1m Typ-1 2m Typ-2 1m Typ-2 2m Typ-3 1m Typ-3 2m Typ-4 1m
##   1        15      119        3       28        3       20        1
##   2         1       88        0       23        0       18        1
##   3         0       65        0       17        0       11        0
##   4         3       49        0       14        0        4        0
##   5         0       41        0        6        0        1        0
##   6         0       16        0        0        0        3        0
##   7         0        4        0        4        0        2        0

each row represents how manny of the items were bought. For example the 4th row in the first column "Typ-1 1m" says that we sold 12 items --> (4*3)

I would like my final output to be across all columns as te summary of each rows, however the number of a row must first multiply with the value in a row.

the output in a first coulmn would look like this: (15*1)+(1*2)+(3*4)=29

I have no idea how to solve this in R.

I have only managed to print out a table.. I would appreciate the help!

Answer 1

We multiply the 'dat' with the row of that and get the column sums ( colSums )

colSums(dat*row(dat))
#   Typ.1_1m Typ.1_2m Typ.2_1m Typ.2_2m Typ.3_1m Typ.3_2m Typ.4_1m 
#      29     1015        3      239        3      142        3