计算 R 中一组变量中值的出现次数(每行) [英] Count occurrences of value in a set of variables in R (per row)

问题描述

假设我有一个包含 10 个数值变量 V1-V10(列)和多行(案例)的数据框.

Let's say I have a data frame with 10 numeric variables V1-V10 (columns) and multiple rows (cases).

我希望 R 做的是:对于每种情况，给我一组变量中某个值出现的次数.

What I would like R to do is: For each case, give me the number of occurrences of a certain value in a set of variables.

例如V2、V3、V6的那一行中数值99出现的次数，显然它的最小值为0(三者都没有99)，最大值为3(全部为三者的值为 99).

For example the number of occurrences of the numeric value 99 in that single row for V2, V3, V6, which obviously has a minimum of 0 (none of the three have the value 99) and a maximum of 3 (all of the three have the value 99).

我真的在寻找相当于 SPSS 函数COUNT:COUNT 创建一个数值变量，对于每种情况，计算相同值的出现次数(或值列表)跨变量列表."

I am really looking for an equivalent to the SPSS function COUNT: "COUNT creates a numeric variable that, for each case, counts the occurrences of the same value (or list of values) across a list of variables."

我想过 table() 和库 plyr 的 count()，但我真的想不通.首选矢量化计算.非常感谢！

I thought about table() and library plyr's count(), but I cannot really figure it out. Vectorized computation preferred. Thanks a lot!

推荐答案

尝试

apply(df,MARGIN=1,table)

其中 df 是您的 data.frame.这将返回一个与 data.frame 中行数相同长度的列表.列表的每一项对应data.frame的一行(顺序相同)，是一张表格，内容是出现次数，名称是对应的值.

Where df is your data.frame. This will return a list of the same length of the amount of rows in your data.frame. Each item of the list corresponds to a row of the data.frame (in the same order), and it is a table where the content is the number of occurrences and the names are the corresponding values.

例如:

df=data.frame(V1=c(10,20,10,20),V2=c(20,30,20,30),V3=c(20,10,20,10))
#create a data.frame containing some data
df #show the data.frame
  V1 V2 V3
1 10 20 20
2 20 30 10
3 10 20 20
4 20 30 10
apply(df,MARGIN=1,table) #apply the function table on each row (MARGIN=1)
[[1]]

10 20 
 1  2 

[[2]]

10 20 30 
 1  1  1 

[[3]]

10 20 
 1  2 

[[4]]

10 20 30 
 1  1  1 

#desired result

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