Coerce a character string to the same type as a target value

Source: R/utils.R

Create a new value from a character string based on an old value, e.g., if the old value is an integer, call as.integer() to coerce the string to an integer.

coerceValue(val, old)

Arguments

val

A character string.
old

An old value, whose type is the target type of val.

Value

A value of the same data type as old if possible.

Details

This function only works with integer, double, date, time (POSIXlt or POSIXct), and factor values. The date must be of the format %Y-%m-%dT%H:%M:%SZ. The factor value must be in the levels of old, otherwise it will be coerced to NA.

Examples

library(DT)
coerceValue("100", 1L)

#> [1] 100
coerceValue("1.23", 3.1416)

#> [1] 1.23
coerceValue("2018-02-14", Sys.Date())

#> [1] "2018-02-14"
coerceValue("2018-02-14T22:18:52Z", Sys.time())

#> [1] "2018-02-14 22:18:52 UTC"
coerceValue("setosa", iris$Species)

#> [1] "setosa"
coerceValue("setosa2", iris$Species)  # NA

#> Warning: New value(s) "setosa2" not in the original factor levels: "setosa, versicolor, virginica"; will be coerced to NA.
#> [1] NA
coerceValue("FALSE", TRUE)  # not supported

#> Warning: The data type is not supported: logical
#> [1] "FALSE"