r元素频率和列名 [英] r element frequency and column name
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问题描述
我有一个包含四列A,B,C和D的数据框:
I have a dataframe that has four columns A, B, C and D:
A B C D
a a b c
b c x e
c d y a
d z
e
f
我想获取所有元素的出现频率以及它们出现的列列表,并按频率排名排序.输出将是这样的:
I would like to get the frequency of all elements and lists of columns they appear, ordered by the frequency ranking. The output would be something like this:
Ranking frequency column
a 1 3 A, B, D
c 1 3 A, B, D
b 2 2 A, C
d 2 2 A, B
e 2 2 A, D
f .....
我将不胜感激. 谢谢!
I would appreciate any help. Thank you!
推荐答案
类似这样的事情:
数据
df <- read.table(header=T, text='A B C D
a a b c
b c x e
c d y a
d NA NA z
e NA NA NA
f NA NA NA',stringsAsFactors=F)
解决方案
#find unique elements
elements <- unique(unlist(sapply(df, unique)))
#use a lapply to find the info you need
df2 <- data.frame(do.call(rbind,
lapply(elements, function(x) {
#find the rows and columns of the elements
a <- which(df == x, arr.ind=TRUE)
#find column names of the elements found
b <- names(df[a[,2]])
#find frequency
c <- nrow(a)
#produce output
c(x, c, paste(b, collapse=','))
})))
#remove NAs
df2 <- na.omit(df2)
#change column names
colnames(df2) <- c('element','frequency', 'columns')
#order according to frequency
df2 <- df2[order(df2$frequency, decreasing=TRUE),]
#create the ranking column
df2$ranking <- as.numeric(factor(df2$frequency,levels=unique(df2$frequency)))
输出:
> df2
element frequency columns ranking
1 a 3 A,B,D 1
3 c 3 A,B,D 1
2 b 2 A,C 2
4 d 2 A,B 2
5 e 2 A,D 2
6 f 1 A 3
8 x 1 C 3
9 y 1 C 3
10 z 1 D 3
如果您希望将element列作为row.names并将排名列作为第一列,您还可以执行以下操作:
And if you want the elements column to be as row.names and the ranking column to be first you can also do:
row.names(df2) <- df2$element
df2$element <- NULL
df2 <- df2[c('ranking','frequency','columns')]
输出:
> df2
ranking frequency columns
a 1 3 A,B,D
c 1 3 A,B,D
b 2 2 A,C
d 2 2 A,B
e 2 2 A,D
f 3 1 A
x 3 1 C
y 3 1 C
z 3 1 D
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