R:对行间隔求和 [英] R: summing over an interval of rows
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问题描述
我是 R 初学者,我需要编写一个函数,在固定间隔(每 4 行)内对数据帧的行进行求和.我试过下面的代码
I'm a beginner R user and I need to write a function that sums the rows of a data frame over a fixed interval (every 4 rows). I've tried the following code
camp<-function(X){
i<-1
n<-nrow(X)
xc<-matrix(nrow=36,ncol=m)
for (i in 1:n){
xc<-apply(X[i:(i+4),],2,sum)
rownames(xc[i])<-rownames(X[i])
i<-i+5
}
return(xc)
}
结果是X[i:(i + 4), ] 中的错误:索引超出范围".我该如何解决?有什么建议吗?
the result is "Error in X[i:(i + 4), ] : index out of range". How can I solve? Any suggestion?
谢谢.
推荐答案
zoo
包有 rollapply
,这对于这样的事情非常方便......
The zoo
package has rollapply
which is pretty handy for stuff like this...
# Make some data
set.seed(1)
m <- matrix( sample( 10 , 32 , repl = TRUE ) , 8 )
# [,1] [,2] [,3] [,4]
#[1,] 3 7 8 3
#[2,] 4 1 10 4
#[3,] 6 3 4 1
#[4,] 10 2 8 4
#[5,] 3 7 10 9
#[6,] 9 4 3 4
#[7,] 10 8 7 5
#[8,] 7 5 2 6
# Sum every 4 rows
require( zoo )
tmp <- rollapply( m , width = 4 , by = 4 , align = "left" , FUN = sum )
# [,1] [,2] [,3] [,4]
#[1,] 23 13 30 12
#[2,] 29 24 22 24
如果您确实想将列聚合为 4 行中的每一行的单个值,您也可以对结果使用 rowSums()
...
You can also use rowSums()
on the result if you actually wanted to aggregate the columns into a single value for each of the 4 rows...
rowSums( tmp )
#[1] 78 99
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