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How to find the sum of every n values in R data frame columns?
To find the sum of every n values in R data frame columns, we can use rowsum function along with rep function that will repeat the sum for rows. For example, if we have a data frame called df that contains 4 columns each containing twenty values then we can find the column sums for every 5 rows by using the command rowsum(df,rep(1:5,each=4)).
Example
Consider the below data frame −
x1<-rpois(20,5) x2<-rpois(20,2) df1<-data.frame(x1,x2) df1
Output
x1 x2 1 7 3 2 9 4 3 7 3 4 3 3 5 9 1 6 4 1 7 7 3 8 4 3 9 6 3 10 5 0 11 4 4 12 5 4 13 5 1 14 6 2 15 1 3 16 1 2 17 6 1 18 6 2 19 1 2 20 8 2
Finding the column sums for every 5 rows in df1 −
Example
rowsum(df1,rep(1:5,each=4))
Output
x1 x2 1 26 13 2 24 8 3 20 11 4 13 8 5 21 7
Example
y1<-rnorm(20) y2<-rnorm(20) y3<-rnorm(20) df2<-data.frame(y1,y2,y3) df2
Output
y1 y2 y3 1 -0.46478980 0.61742170 -0.21406143 2 1.42820694 -1.68668632 -1.69183062 3 -1.09014651 -0.80538397 -1.73060665 4 0.04143155 -0.86250648 -0.50698176 5 1.31066192 1.98317492 0.81144732 6 1.05362995 1.31032857 -0.48538293 7 1.13221772 3.27862204 -1.42116882 8 -2.30864576 -0.02998736 -0.35898649 9 -1.30371212 0.26152070 -0.25968593 10 -0.93208053 0.59726153 0.31393063 11 0.23612475 1.72240765 -2.21882009 12 0.58740869 0.53739269 0.52578465 13 0.42427296 -0.84617072 -0.35684917 14 -0.33885432 0.09297437 -0.61340922 15 -0.40246042 -0.94370468 0.01108134 16 -0.97853686 1.08559425 0.71596796 17 0.28577367 -0.57999260 -0.14349388 18 -0.78154458 -2.40582173 2.50692776 19 0.05791671 0.94479521 0.79723502 20 -0.03289249 -1.46621425 -0.89169830
Example
Finding the column sums for every 5 rows in df2 −
rowsum(df2,rep(1:5,each=4))
Output
y1 y2 y3 1 -0.08529781 -2.7371551 -4.1434804 2 1.18786383 6.5421382 -1.4540909 3 -1.41225921 3.1185826 -1.6387907 4 -1.29557865 -0.6113068 -0.2432091 5 -0.47074670 -3.5072334 2.2689706
Updated on: 16-Mar-2021
2K+ Views
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