Sum by Rows in R

Question

Let me reclaim my question, how I can sum the numbers by row, and list the sum follow by the last column, forming a new column like the second table (sum = a + b+ c + d + e)?

And I also want to know what if some of the values are N/A, can I still treat them as numbers?

Sample input:

     a          b           c          d            e
1    90         67          18         39           74
2    100        103         20         45           50 
3    80         87          23         44           89
4    95         57          48         79           90
5    74         81          61         95           131

Desired output:

     a          b           c          d            e    sum
1    90         67          18         39           74   288
2    100        103         20         45           50   318
3    80         87          23         44           89   323
4    95         57          48         79           90   369
5    74         81          61         95           131  442 

Answer 1

To add a row sum, you can use addmargins

M <- matrix(c(90,67,18,39,74), nrow=1)
addmargins(M, 2)   #2 = row margin
#      [,1] [,2] [,3] [,4] [,5] [,6]
# [1,]   90   67   18   39   74  288

If you have missing data, you'll need to change the margin function to something that will properly handle the NA values

M<-matrix(c(90,67,18,NA,74), nrow=1)
addmargins(M, 2, FUN=function(...) sum(..., na.rm=T))
#      [,1] [,2] [,3] [,4] [,5] [,6]
# [1,]   90   67   18   NA   74  249