How to create a variable where the value is taken from another variable matching values of a vector-CodePudding

I have a dataframe with a variable that is composed of strings of product's names. Ex.:

| Names                       | Price ...|
|-----------------------------|----------|
| milk                        | ...      |
| pizza with tomato           | ...      |
| tuna with olive and beans   | ...      |
| etc...                      | ...      |

I would like to create an other variable that take as values names stored in a vector that match those in variable Names

Basically, if I have a vector:

x <- c("milk", "pizza", "tuna")

The code should look into the variable Names and if it finds a match in vector x then it takes that value and stores it in a new variable called tag that should have as values milk, pizza, tuna.

Is it possible to create a variable whose values are taken from another variable if conditions are met?

CodePudding user response：

If I am understanding correctly, you want to have a tag (like a keyword) in a new column in your dataframe. If so, then it is probably easier to just extract the word if it occurs in your search list using str_extract.

library(stringr)

search <- c("milk", "pizza", "tuna")    

df$tag <- stringr::str_extract(df$Names, paste(search, collapse="|"))

Output

                       Names price   tag
1                       milk  3.99  milk
2          pizza with tomato  5.99 pizza
3 tuna with olives and beans  9.99  tuna
4                       crab  4.99  <NA>

Data

df <-
  structure(list(
    Names = c("milk", "pizza with tomato", "tuna with olives and beans",
              "crab"),
    price = c(3.99, 5.99, 9.99, 4.99),
    tag = c("milk", "pizza",
            "tuna", NA)
  ),
  row.names = c(NA,-4L),
  class = "data.frame")