How to find the sum of column values of an R data frame?

An R data frame contain columns that might represent a similar type of variables; therefore, we might want to find the sum of the values for each of the columns and make a comparison based on the sum. This can be done with the help of sum function but first we need to extract the columns to find the sum.

Example

Consider the below data frame −

> set.seed(1) > x1<-rnorm(20) > x2<-rnorm(20,0.5) > x3<-rnorm(20,1) > x4<-rnorm(20,1.5) > x5<-rnorm(20,2) > x6<-rnorm(20,2.5) > x7<-rnorm(20,3) > df<-data.frame(x1,x2,x3,x4,x5,x6,x7) > df x1 x2 x3 x4 x5 x6 x7 1 -0.62645381 1.41897737 0.83547640 3.9016178 1.4313313 1.879633 2.494043 2 0.18364332 1.28213630 0.74663832 1.4607600 1.8648214 2.542116 4.343039 3 -0.83562861 0.57456498 1.69696338 2.1897394 3.1780870 1.589078 2.785421 4 1.59528080 -1.48935170 1.55666320 1.5280022 0.4764332 2.658029 2.820443 5 0.32950777 1.11982575 0.31124431 0.7567268 2.5939462 1.845415 2.899809 6 -0.82046838 0.44387126 0.29250484 1.6887923 2.3329504 4.267287 3.712666 7 0.48742905 0.34420449 1.36458196 -0.3049586 3.0630998 3.216707 2.926436 8 0.73832471 -0.97075238 1.76853292 2.9655549 1.6958161 3.410174 2.962366 9 0.57578135 0.02184994 0.88765379 1.6532533 2.3700188 2.884185 2.318340 10 -0.30538839 0.91794156 1.88110773 3.6726117 2.2670988 4.182176 2.675730 11 1.51178117 1.85867955 1.39810588 1.9755095 1.4574800 1.864264 3.060160 12 0.38984324 0.39721227 0.38797361 0.7900536 3.2078678 2.038355 2.411106 13 -0.62124058 0.88767161 1.34111969 2.1107264 3.1604026 3.932282 3.531496 14 -2.21469989 0.44619496 -0.12936310 0.5659024 2.7002136 1.849304 1.481606 15 1.12493092 -0.87705956 2.43302370 0.2463666 3.5868335 2.292619 3.306558 16 -0.04493361 0.08500544 2.98039990 1.7914462 2.5584864 2.107192 1.463550 17 -0.01619026 0.10571005 0.63277852 1.0567081 0.7234078 2.180007 2.699024 18 0.94383621 0.44068660 -0.04413463 1.5011054 1.4267346 2.220887 2.471720 19 0.82122120 1.60002537 1.56971963 1.5743413 0.7753874 2.994188 2.347905 20 0.59390132 1.26317575 0.86494540 0.9104791 1.5265994 2.322670 2.943103

Finding the sum of all columns one by one −

> sum(df$x1) [1] 3.810478 > sum(df$x2) [1] 9.87057 > sum(df$x3) [1] 22.77594 > sum(df$x4) [1] 32.03474 > sum(df$x5) [1] 42.39702 > sum(df$x6) [1] 52.27657 > sum(df$x7) [1] 55.65452

Let’s have a look at one more example −

> y1<-1:10 > y2<-11:20 > y3<-rep(c(1,2,3,4,5),times=2) > df_y<-data.frame(y1,y2,y3) > df_y   y1 y2 y3  1 1 11 1  2 2 12 2  3 3 13 3  4 4 14 4  5 5 15 5  6 6 16 1  7 7 17 2  8 8 18 3  9 9 19 4 10 10 20 5 > sum(df_y$y1) [1] 55 > sum(df_y$y2) [1] 155 > sum(df_y$y3) [1] 30