Using dplyr to conditionally replace values in a column

In dplyr and tidyr

dat %>% 
    mutate(var = replace(var, var != "Candy", "Not Candy"))

Significantly faster than the ifelse approaches. Code to create the initial dataframe can be as below:

library(dplyr)
dat <- as_data_frame(c("Candy","Sanitizer","Candy","Water","Cake","Candy","Ice Cream","Gum","Candy","Coffee"))
colnames(dat) <- "var"

Assuming your data frame is dat and your column is var:

dat = dat %>% mutate(candy.flag = factor(ifelse(var == "Candy", "Candy", "Non-Candy")))

Another solution with dplyr using case_when:

dat %>%
    mutate(var = case_when(var == 'Candy' ~ 'Candy',
                           TRUE ~ 'Non-Candy'))

The syntax for case_when is condition ~ value to replace. Documentation here.

Probably less efficient than the solution using replace, but an advantage is that multiple replacements could be performed in a single command while still being nicely readable, i.e. replacing to produce three levels:

dat %>%
    mutate(var = case_when(var == 'Candy' ~ 'Candy',
                           var == 'Water' ~ 'Water',
                           TRUE ~ 'Neither-Water-Nor-Candy'))