R语言中的函数23：zoo::rollmean, rollmax, rollmedian, rollsum等等

函数介绍

rollmean(x, k, fill = if (na.pad) NA, na.pad = FALSE, 
  align = c("center", "left", "right"), ...)
  
rollmax(x, k, fill = if (na.pad) NA, na.pad = FALSE, 
  align = c("center", "left", "right"), ...)


rollmedian(x, k, fill = if (na.pad) NA, na.pad = FALSE, 
  align = c("center", "left", "right"), ...)

rollsum(x, k, fill = if (na.pad) NA, na.pad = FALSE, 
  align = c("center", "left", "right"), ...)

rollmeanr(..., align = "right")
rollmaxr(..., align = "right")
rollmedianr(..., align = "right")
rollsumr(..., align = "right")

• x: 是一个序列。
• k: 滑动窗口的宽度，对于rollmedian函数必须是个奇数。
• fill: 是一个三个元素的向量或者是一个list, 提供在数据左边/中间/右边的填充数据。
• na.pad: 不建议使用的命令。用fill=NA来代替na.pad=TRUE
• align: 接受一个字符串（left, center, right）来确定结果是左边滚动、右边滚动或者是中间滚动。
• rollxxxr:表示align='right’的情形
• 默认情况下align=‘center’

rollmean()

x=1:10
rollmean(x,k=3,fill = c(-1,-2,-3),align = 'left')
# [1]  2  3  4  5  6  7  8  9 -3 -3
rollmean(x,k=3,fill = c(-1,-2,-3),align = 'center')
# [1] -1  2  3  4  5  6  7  8  9 -3
rollmean(x,k=3,fill = c(-1,-2,-3),align = 'right')
[1] -1 -1  2  3  4  5  6  7  8  9

rollmax()

x=1:10
rollmax(x,k=3,fill = c(-1,-2,-3),align = 'left')
# [1]  3  4  5  6  7  8  9 10 -3 -3
rollmax(x,k=3,fill = c(-1,-2,-3),align = 'center')
# [1] -1  3  4  5  6  7  8  9 10 -3
rollmax(x,k=3,fill = c(-1,-2,-3),align = 'right')
# [1] -1 -1  3  4  5  6  7  8  9 10

rollmedian

x=1:10
rollmedian(x,k=3,fill = c(-1,-2,-3),align = 'left')
# [1]  3  4  5  6  7  8  9 10 -3 -3
rollmedian(x,k=3,fill = c(-1,-2,-3),align = 'center')
# [1] -1  2  3  4  5  6  7  8  9 -3
rollmedian(x,k=3,fill = c(-1,-2,-3),align = 'right')
# [1] -1 -1  2  3  4  5  6  7  8  9

rollsum

x=1:10
rollsum(x,k=3,fill = c(-1,-2,-3),align = 'left')
# [1]  6  9 12 15 18 21 24 27 -3 -3
rollsum(x,k=3,fill = c(-1,-2,-3),align = 'center')
# [1] -1  6  9 12 15 18 21 24 27 -3
rollsum(x,k=3,fill = c(-1,-2,-3),align = 'right')
# [1] -1 -1  6  9 12 15 18 21 24 27