Ignore NA in vector sum

Question

I want to know if is there a way to handle NA values when I try to sum some columns from a data frame?

This is a simulated example of the data I am working with:

id<-rep(1:4,each=8)
v1<-c(1,2,5,4,58,6,4,9)
v2<-c(78,85,56,47,12,3,65,98)
v3<-c(101,NA,452,NA,NA,45,7,56)
data<-data.frame(id,v1,v2,v3)
data
  id v1 v2  v3
1  1  1 78 101
2  1  2 85  NA
3  2  5 56 452
4  2  4 47  NA
5  3 58 12  NA
6  3  6  3  45
7  4  4 65   7
8  4  9 98  56

I wanto apply this formula using v1,v2,v3:

data$cat<-v1*0.05+v2*0.05+v3*0.05

This is the result I get when I use the sum:

data
  id v1 v2  v3   cat
1  1  1 78 101  9.00
2  1  2 85  NA    NA
3  2  5 56 452 25.65
4  2  4 47  NA    NA
5  3 58 12  NA    NA
6  3  6  3  45  2.70
7  4  4 65   7  3.80
8  4  9 98  56  8.15

v1,v2 and v3 are numeric vectors

Answer 1

You can try rowSums with na.rm = TRUE (as @akrun said in the comment) like below

data$cat <- rowSums(data[-1] * c(0.05, 0.05, 0.05)[col(data[-1])], na.rm = TRUE)

which gives

> data
   id v1 v2  v3   cat
1   1  1 78 101  9.00
2   1  2 85  NA  4.35
3   1  5 56 452 25.65
4   1  4 47  NA  2.55
5   1 58 12  NA  3.50
6   1  6  3  45  2.70
7   1  4 65   7  3.80
8   1  9 98  56  8.15
9   2  1 78 101  9.00
10  2  2 85  NA  4.35
11  2  5 56 452 25.65
12  2  4 47  NA  2.55
13  2 58 12  NA  3.50
14  2  6  3  45  2.70
15  2  4 65   7  3.80
16  2  9 98  56  8.15
17  3  1 78 101  9.00
18  3  2 85  NA  4.35
19  3  5 56 452 25.65
20  3  4 47  NA  2.55
21  3 58 12  NA  3.50
22  3  6  3  45  2.70
23  3  4 65   7  3.80
24  3  9 98  56  8.15
25  4  1 78 101  9.00
26  4  2 85  NA  4.35
27  4  5 56 452 25.65
28  4  4 47  NA  2.55
29  4 58 12  NA  3.50
30  4  6  3  45  2.70
31  4  4 65   7  3.80
32  4  9 98  56  8.15

Answer 2

For calculation purpose you can turn NA to 0.

data$cat <- with(replace(data, is.na(data), 0), v1*0.05 + v2*0.05 + v3*0.05)
data

#   id v1 v2  v3   cat
#1   1  1 78 101  9.00
#2   1  2 85  NA  4.35
#3   1  5 56 452 25.65
#4   1  4 47  NA  2.55
#5   1 58 12  NA  3.50
#6   1  6  3  45  2.70
#7   1  4 65   7  3.80
#8   1  9 98  56  8.15
#9   2  1 78 101  9.00
#10  2  2 85  NA  4.35
#11  2  5 56 452 25.65
#12  2  4 47  NA  2.55
#13  2 58 12  NA  3.50
#14  2  6  3  45  2.70
#15  2  4 65   7  3.80
#...
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