col_types

• One approach is to tell readr that x is a numeric column using col_types argument:

df <- read_csv(
  simple_csv, 
  col_types = list(x = col_double())
)

## Warning: One or more parsing issues, call `problems()` on your data frame for details,
## e.g.:
##   dat <- vroom(...)
##   problems(dat)

• read_csv() reports that there was a problem, and tells us we can find out more with problems()

problems(df)

## # A tibble: 1 × 5
##     row   col expected actual file                            
##   <int> <int> <chr>    <chr>  <chr>                           
## 1     3     1 a double .      /tmp/Rtmpy0p0xj/file179469876801