有没有办法一次重新编码多个变量? [英] Is there a way to recode multiple variables at once?

问题描述

我有一个学生成绩单分数的数据集，范围从 D- 到 A+.我想将它们重新编码为 1-12 的比例(即 D- = 1，D = 2 ... A = 11，A+ = 12).现在我正在起诉 plyr 中的 revalue 函数.我有几列要重新编码 - 是否有比在每列上运行 revalue 更短的方法?

I have a dataset of students' report card marks that range from D- to A+. I'd like to recode them into scale of 1-12 (i.e. D- = 1, D = 2 ... A = 11, A+ = 12). Right now I'm suing the revalue function in plyr. I have several columns that I'd like to recode - is there a shorter way to do this than running revalue on each column?

一些数据:

student  <- c("StudentA","StudentB","StudentC","StudentD","StudentE","StudentF","StudentG","StudentH","StudentI","StudentJ")
read <- c("A", "A+", "B", "B-", "A", "C", "C+", "D", "C", "B+")
write <- c("A-", "B", "C", "C+", "D", "B-", "B", "C", "D+", "B")
math <- c("C", "C", "D+", "A", "A+", "B", "B-", "C-", "D+", "C")

df <- data.frame (student, read, write, math)

现在我正在像这样重新编码它们:

Right now I'm recoding them like this:

df$read.r <- as.numeric (revalue (df$read, c("D-" = "1",
                             "D" = "2",
                             "D+" = "3",
                             "C-" = "4",
                             "C" = "5",
                             "C+" = "6",
                             "B-" = "7",
                             "B" = "8",
                             "B+" = "9",
                             "A-" = "10",
                             "A" = "11",
                             "A+" = "12"
                             )))

有没有更好的方法而不是运行 3 次(或更多)?所有列都具有相同的值.

Instead of running this 3 times (or more) is there a better way? All of the columns have identical values.

推荐答案

 df1 <- df[,-1]

df1[] <- as.numeric(factor(unlist(df[,-1]), 
         levels=paste0(rep(LETTERS[4:1], each=3), c("-", "", "+"))))
cbind(df, setNames(df1, paste(colnames(df1), "r", sep=".")))
#       student read write math read.r write.r math.r
#1  StudentA    A    A-    C     11      10      5
#2  StudentB   A+     B    C     12       8      5
#3  StudentC    B     C   D+      8       5      3
#4  StudentD   B-    C+    A      7       6     11
#5  StudentE    A     D   A+     11       2     12
#6  StudentF    C    B-    B      5       7      8
#7  StudentG   C+     B   B-      6       8      7
#8  StudentH    D     C   C-      2       5      4
#9  StudentI    C    D+   D+      5       3      3
#10 StudentJ   B+     B    C      9       8      5

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