Sum by Rows in R

1
votes

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
3
rsum
You can post your code directly without needing to post an image - LinkBerest
Just did, not code though. - Bobby
@MrFlick answer of using rowsum with addmargins is the standard answer if that doesn't work post the code that you've tried and an explanation of the problem your having with it - LinkBerest

3 Answers

5
votes

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
1
votes

Consider using apply(). For example:

set.seed(10) # optional, but this command will replicate data as shown

# create some data
x <-matrix(rnorm(1:25),nrow=5,ncol=5) # 5x5 matrix of random numbers
x
            [,1]       [,2]       [,3]        [,4]       [,5]
[1,]  0.01874617  0.3897943  1.1017795  0.08934727 -0.5963106
[2,] -0.18425254 -1.2080762  0.7557815 -0.95494386 -2.1852868
[3,] -1.37133055 -0.3636760 -0.2382336 -0.19515038 -0.6748659
[4,] -0.59916772 -1.6266727  0.9874447  0.92552126 -2.1190612
[5,]  0.29454513 -0.2564784  0.7413901  0.48297852 -1.2651980

x.sum <-apply(x,1,sum) # sum the rows. Note: apply(x,2,sum) sums cols

x.sum
[1]  1.003356605 -3.776777904 -2.843256446 -2.431935624 -0.002762636

# attach new column (x.sum) to matrix x  
x.sum.1 <-cbind(x,x.sum)

x.sum.1
                                                                    x.sum
[1,]  0.01874617  0.3897943  1.1017795  0.08934727 -0.5963106  1.003356605
[2,] -0.18425254 -1.2080762  0.7557815 -0.95494386 -2.1852868 -3.776777904
[3,] -1.37133055 -0.3636760 -0.2382336 -0.19515038 -0.6748659 -2.843256446
[4,] -0.59916772 -1.6266727  0.9874447  0.92552126 -2.1190612 -2.431935624
[5,]  0.29454513 -0.2564784  0.7413901  0.48297852 -1.2651980 -0.002762636
0
votes

Let's say you have the dataframe df, then you could try something like this:

# Assuming the columns a,b,c,d,e are at indices 1:5
df$sum = rowSums(df[ , c(1:5)], na.rm = T)

Or you could aslo try this:

transform(df, sum=rowSums(df), na.rm = T)