Finding out if cells in a data frame column contain a specific character in R

Question

I want to find out if cells in a data frame column contain a specific character in R.

I created a column called df1$var_sting using the code below:

df1 <- data.frame(
  var_sting = 
    c(
    "test1",
    "test2 + test3"
    )
  )

I want to create a column called df1$plus_test_short, which contains a "yes/no" answer to the question on whether a character ("+") is present in the variable called "df1$var_sting".

I can do this the long way, using the code below:

df1$plus_test_long <- 
  c(
    "no",
    "yes"
  )

When I try to do this the short way, using the grepl() command, it does not give the desired result:

> df1$plus_test_short
[1] "yes" "yes"

Is there any way to do this using a short way, that does not require me to input results individually in the plus_test_ prefixed columns that correspond to the appropriate rows in the df1$var_sting variable?

Please advise. Thanks a head of time.

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# stackoverflow example data

## creates object
df1 <- data.frame(
  var_sting = 
    c(
    "test1",
    "test2 + test3"
    )
  )

### displays object
df1

## desired new column, which tells if there is a + (plus sign) in the cell

### done the long way, which requires manual input
df1$plus_test_long <- 
  c(
    "no",
    "yes"
  )

## done the short way, using grepl() command, which does not require manual entering of "yes" and "no" with each cell in corresponding column
df1$plus_test_short <- 
  ifelse(((grepl("+", df1$var_sting)) == TRUE), "yes", "no")
df1$plus_test_short
# ---- NOTE: does not work

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