R：按行间隔求和

我是一个初学者，需要编写一个函数，在固定的时间间隔（每4行）对数据帧的行进行求和。 我尝试了以下代码

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)
}

---

camp这里有一种方法：

## Sample data
m <- matrix(1:36, nrow=12)
## Create a "group" index
fac <- (seq_len(nrow(m))-1) %/% 4
## Apply sum 
apply(m, 2, function(v) tapply(v, fac, sum))

结果:

  [,1] [,2] [,3]
0   10   58  106
1   26   74  122
2   42   90  138

以下是一种方法：

## Sample data
m <- matrix(1:36, nrow=12)
## Create a "group" index
fac <- (seq_len(nrow(m))-1) %/% 4
## Apply sum 
apply(m, 2, function(v) tapply(v, fac, sum))

结果:

  [,1] [,2] [,3]
0   10   58  106
1   26   74  122
2   42   90  138

以下是一种方法：

## Sample data
m <- matrix(1:36, nrow=12)
## Create a "group" index
fac <- (seq_len(nrow(m))-1) %/% 4
## Apply sum 
apply(m, 2, function(v) tapply(v, fac, sum))

结果:

  [,1] [,2] [,3]
0   10   58  106
1   26   74  122
2   42   90  138

以下是一种方法：

## Sample data
m <- matrix(1:36, nrow=12)
## Create a "group" index
fac <- (seq_len(nrow(m))-1) %/% 4
## Apply sum 
apply(m, 2, function(v) tapply(v, fac, sum))

结果:

  [,1] [,2] [,3]
0   10   58  106
1   26   74  122
2   42   90  138

zoo
软件包有
rollapply
，这对于像这样的东西非常方便

#  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

zoo
软件包有
rollapply
，这对于像这样的东西非常方便

#  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

zoo
软件包有
rollapply
，这对于像这样的东西非常方便

#  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

zoo
软件包有
rollapply
，这对于像这样的东西非常方便

#  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

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