R对特定数据框列的Apply()函数 [英] R Apply() function on specific dataframe columns
本文介绍了R对特定数据框列的Apply()函数的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我想在数据框上使用apply函数,但只将函数应用于最后5列.
I want to use the apply function on a dataframe, but only apply the function to the last 5 columns.
B<- by(wifi,(wifi$Room),FUN=function(y){apply(y, 2, A)})
这会将A应用于y的所有列
This applies A to all the columns of y
B<- by(wifi,(wifi$Room),FUN=function(y){apply(y[4:9], 2, A)})
这仅将A应用于y的第4-9列,但B的总收益去除了前3列...我仍然想要那些,我只是不想将A应用于它们.
This applies A only to columns 4-9 of y, but the total return of B strips off the first 3 columns... I still want those, I just don't want A applied to them.
wifi[,1:3]+B
也没有按照我的期望/要求做.
also does not do what I expected/wanted.
推荐答案
使用示例data.frame和示例函数(对所有值仅+1)
Using an example data.frame and example function (just +1 to all values)
A <- function(x) x + 1
wifi <- data.frame(replicate(9,1:4))
wifi
# X1 X2 X3 X4 X5 X6 X7 X8 X9
#1 1 1 1 1 1 1 1 1 1
#2 2 2 2 2 2 2 2 2 2
#3 3 3 3 3 3 3 3 3 3
#4 4 4 4 4 4 4 4 4 4
data.frame(wifi[1:3], apply(wifi[4:9],2, A) )
#or
cbind(wifi[1:3], apply(wifi[4:9],2, A) )
# X1 X2 X3 X4 X5 X6 X7 X8 X9
#1 1 1 1 2 2 2 2 2 2
#2 2 2 2 3 3 3 3 3 3
#3 3 3 3 4 4 4 4 4 4
#4 4 4 4 5 5 5 5 5 5
甚至:
data.frame(wifi[1:3], lapply(wifi[4:9], A) )
#or
cbind(wifi[1:3], lapply(wifi[4:9], A) )
# X1 X2 X3 X4 X5 X6 X7 X8 X9
#1 1 1 1 2 2 2 2 2 2
#2 2 2 2 3 3 3 3 3 3
#3 3 3 3 4 4 4 4 4 4
#4 4 4 4 5 5 5 5 5 5
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