I would like to execute a logical operation using a character string (yes I want to do it this way)
a = data.frame(x=c(1,2,3,4),y=c(11,12,13,14))
logical_text = "a$x!=2 & a$y!=14"
a
> a
x y
1 1 11
2 2 12
3 3 13
4 4 14
I am hoping to use the string as follows
a[logical_text,]
> a[logical_text,]
x y
NA NA NA
In order to get the same result as:
a[a$x!=2 & a$y!=14,]
> a[a$x!=2 & a$y!=14,]
x y
1 1 11
3 3 13
It's not necessarily a good idea to do things this way. But if you really must you can use eval(parse(text = your_command_as_a_string_here)) to evaluate a string as if it were code
a = data.frame(x=c(1,2,3,4),y=c(11,12,13,14))
logical_text = "a$x!=2 & a$y!=14"
# Evaluate logical_text into a temporary logical variable
logical_output <- eval(parse(text = logical_text))
a[logical_output,]
# x y
#1 1 11
#3 3 13
# Same thing but without storing as a temporary variable.
a[eval(parse(text=logical_text)), ]
# x y
#1 1 11
#3 3 13
