根据其他列中的条件更新一列中的值

Question

如果我的数据框(df)如下所示:

Name        State
John Smith  MI
John Smith  WI
Jeff Smith  WI

我想从WI"John Smith1"重命名John Smith.什么是SQL语句中最干净的R等价物？

update df 
set Name = "John Smith1"
where Name = "John Smith"
and State = "WI"

Answer 1

df <- data.frame(Name=c('John Smith', 'John Smith', 'Jeff Smith'),
                 State=c('MI','WI','WI'), stringsAsFactors=F)

df <- within(df, Name[Name == 'John Smith' & State == 'WI'] <- 'John Smith1')

> df
         Name State
1  John Smith    MI
2 John Smith1    WI
3  Jeff Smith    WI

Answer 2

单程:

df[df$Name == "John_Smith" & df$State == "WI", "Name"] <- "John_Smith1"

使用的另一种方式dplyr:

df %>% mutate(Name = ifelse(State == "WI" & Name == "John_Smith", "John_Smith1", Name))

注意:正如David Arenburg所说,第一栏不应该是一个因素.为此,读取数据集stringsAsFactors = FALSE.