R 从几个具有重叠值的列中创建唯一值的向量

在我的data.frame中，一行的主题有三列。我想要一个额外的列，每行有一个唯一的主题。首先，我的数据看起来如何：

DATE <- c("1","2","3","4","5","6","7","1","2","3","4","5","6","7")
COMP <- c("A", "A", "A", "A", "A", "A", "A", "B", "B", "B", "B", "B", "B", "B")
RET <- c(-2.0,1.1,3,1.4,-0.2, 0.6, 0.1, -0.21, -1.2, 0.9, 0.3, -0.1,0.3,-0.12)
CLASS <- c("positive", "negative", "aneutral", "positive", "positive", "negative", "aneutral", "positive", "negative", "negative", "positive", "aneutral", "aneutral", "aneutral")
SUBJECT.1 <- c("LITIGATION","LAYOFF","POLLUTION","CHEMICAL DISASTER","PRESS RELEASE","PEOPLE","EMISSIONS","ENERGY","WASTE MANAGEMENT","EMPLOYEES","MANAGEMENT","PRESS RELEASE","HOTELS","POLLUTION")
SUBJECT.2 <- c("POLLUTION","EMPLOYEES","NUCLEAR","FUELS","STOCK OPTION PLAN","EXECUTIVES","CO2","SOLAR","POLLUTION","EXECUTIVES","PRESS RELEASE","CELEBRITIES","CELEBRITIES","LITIGATION")
SUBJECT.3 <- c("ENVIRONMENT","JOB REDUCTIONS","POWER PLANTS","POLLUTION","EMPLOYEES","FRAUD","CLIMATE CHANGE","SUSTAINABILITY","HAZARDOUS WASTE","BONUS PAY","LITIGATION","EMISSIONS","SCANDALS","SCANDALS")
CONTROLVAR <- c("11","13","13","14","13","14","12","11","13","13","14","13","14","12")

mydf <- data.frame(DATE, COMP, RET, CLASS, SUBJECT.1, SUBJECT.2, SUBJECT.3, CONTROLVAR, stringsAsFactors=F)

mydf

#    DATE COMP   RET    CLASS         SUBJECT.1         SUBJECT.2       SUBJECT.3 CONTROLVAR
# 1     1    A -2.00 positive        LITIGATION         POLLUTION     ENVIRONMENT         11
# 2     2    A  1.10 negative            LAYOFF         EMPLOYEES  JOB REDUCTIONS         13
# 3     3    A  3.00 aneutral         POLLUTION           NUCLEAR    POWER PLANTS         13
# 4     4    A  1.40 positive CHEMICAL DISASTER             FUELS       POLLUTION         14
# 5     5    A -0.20 positive     PRESS RELEASE STOCK OPTION PLAN       EMPLOYEES         13
# 6     6    A  0.60 negative            PEOPLE        EXECUTIVES           FRAUD         14
# 7     7    A  0.10 aneutral         EMISSIONS               CO2  CLIMATE CHANGE         12
# 8     1    B -0.21 positive            ENERGY             SOLAR  SUSTAINABILITY         11
# 9     2    B -1.20 negative  WASTE MANAGEMENT         POLLUTION HAZARDOUS WASTE         13
# 10    3    B  0.90 negative         EMPLOYEES        EXECUTIVES       BONUS PAY         13
# 11    4    B  0.30 positive        MANAGEMENT     PRESS RELEASE      LITIGATION         14
# 12    5    B -0.10 aneutral     PRESS RELEASE       CELEBRITIES       EMISSIONS         13
# 13    6    B  0.30 aneutral            HOTELS       CELEBRITIES        SCANDALS         14
# 14    7    B -0.12 aneutral         POLLUTION        LITIGATION        SCANDALS         12

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谢谢大家!

mydf$SUBJECT这里有两行解决方案，只需将3
ifelse（）链接在一起即可

mydf$SUBJECT <- "OTHER"
sapply(c("SUBJECT.3", "SUBJECT.2", "SUBJECT.1"), function(x) mydf[mydf[, x] %in% c("LITIGATION", "POLLUTION", "LAYOFF", "EMISSIONS"), "SUBJECT"] <<- mydf[mydf[, x] %in% c("LITIGATION", "POLLUTION", "LAYOFF", "EMISSIONS"), x])
mydf$SUBJECT[mydf$SUBJECT == "EMISSIONS"] <- "POLLUTION"

重要的是，您似乎需要首先将排放量更改为污染。@初学者我在结尾将排放量更改为污染量，尽管我在结尾添加了额外的一行（当我看到cptn希望将污染与排放量合并时），我承认这一点我忘了把它添加到
重要的
向量中。@David Arenburg:谢谢你的回答！也可以只使用部分单词进行分组吗。这可能是一个坏例子，但假设我希望包含“emis”、“WAST”和“POLLU”的每个值最终都变成污染。这是否有可能融入到您的方法中？我肯定‘grepl（）’会起作用，但不知道具体怎么做……我现在没有时间（在工作中）修改它，我可以今晚晚些时候再看。同时看看@agstudy-answer，他在那里使用regex
mydf$SUBJECT <- "OTHER"
sapply(c("SUBJECT.3", "SUBJECT.2", "SUBJECT.1"), function(x) mydf[mydf[, x] %in% c("LITIGATION", "POLLUTION", "LAYOFF", "EMISSIONS"), "SUBJECT"] <<- mydf[mydf[, x] %in% c("LITIGATION", "POLLUTION", "LAYOFF", "EMISSIONS"), x])
mydf$SUBJECT[mydf$SUBJECT == "EMISSIONS"] <- "POLLUTION"

ifelse( mydf$SUBJECT.1 %in% important, mydf$SUBJECT.1,
       ifelse( mydf$SUBJECT.2 %in% important, mydf$SUBJECT.2,
             ifelse( mydf$SUBJECT.3 %in% important, mydf$SUBJECT.3,'OTHER')))