如何获得前10个最高值的变量的列名？

如果我有一个data.frame（sum_clus）有600列（变量）和10行没有NA和都是数值，我如何创建5个新变量，给我的前5个变量的列名称那一排？如何获得前10个最高值的变量的列名？

例如，

max <- apply(sum_clus ,1, max)  
for(ii in 1:10) sum_clus$max[ii] <- colnames(sum_clus)[which(sum_clus[ii , ] 
== sum_clus[ii, sum_clus[ii,] == max[ii]])]

这上面的代码帮我创建一个变量$ sum_clus最大，给了我各行中的最大变量的列名。同样，我怎么能得到5个这样的变量，给我的前5个变量的列名称？ sum_clus $ max，sum_clus $ second_but_max等。

在此先感谢！

来源

2013-05-14 Shreyes

你能提供一个样本？也许'sum_clus [1：10,1：10]'或什么...？ – Frank

下面是一个类似的解决方案，使用（i）代替apply的循环;和（ii）rank而不是order。

set.seed(1) 
n_i = 10 
n_ii = 600 
n_top = 5 
df <- data.frame(matrix(runif(n_ii*n_i), ncol = n_ii)) 

out <- matrix("",n_top,n_i) 
for (i in 1:n_i){ 
    colranks <- rank(df[i,]) 
    out[,i] <- names(sort(colranks)[n_ii:(n_ii-(n_top-1))]) 
} 
#  [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] 
# [1,] "X369" "X321" "X348" "X415" "X169" "X258" "X55" "X182" "X99" "X78" 
# [2,] "X42" "X295" "X563" "X173" "X377" "X31" "X246" "X353" "X259" "X384" 
# [3,] "X98" "X440" "X371" "X207" "X429" "X292" "X433" "X437" "X123" "X558" 
# [4,] "X13" "X193" "X396" "X78" "X543" "X228" "X211" "X2" "X583" "X508" 
# [5,] "X35" "X364" "X249" "X33" "X388" "X405" "X458" "X252" "X569" "X456"

一行程序模拟与apply是

apply(df,1,function(x)names(sort(rank(x))))[600:596,]

来源

2013-05-14 19:37:39 Frank

你的循环在哪里？ –

@RicardoSaporta我已经用完整的答案覆盖了我的解决方案。 – Frank

我更喜欢没有循环; –

一种选择是使用order()，然后用它来子集的列名，如：

set.seed(1) 
df <- data.frame(matrix(runif(600*10), ncol = 600)) 

foo <- function(x, names) { 
    ord <- order(x, decreasing = TRUE)[1:5] 
    names[ord] 
} 

nams <- colnames(df) 
apply(df, 1, foo, names = nams)

生产

> apply(df, 1, foo, names = nams) 
    [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] 
[1,] "X369" "X321" "X348" "X415" "X169" "X258" "X55" "X182" "X99" "X78" 
[2,] "X42" "X295" "X563" "X173" "X377" "X31" "X246" "X353" "X259" "X384" 
[3,] "X98" "X440" "X371" "X207" "X429" "X292" "X433" "X437" "X123" "X558" 
[4,] "X13" "X193" "X396" "X78" "X543" "X228" "X211" "X2" "X583" "X508" 
[5,] "X35" "X364" "X249" "X33" "X388" "X405" "X458" "X252" "X569" "X456"

检查工作的：

> names(sort(unlist(df[1,, drop = TRUE]), decreasing = TRUE)[1:5]) 
[1] "X369" "X42" "X98" "X13" "X35" 
> names(sort(unlist(df[2,, drop = TRUE]), decreasing = TRUE)[1:5]) 
[1] "X321" "X295" "X440" "X193" "X364"

似乎确定。

来源

2013-05-14 19:37:00

如何获得前10个最高值的变量的列名？

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