save conditions in a list

Hello,

I'm not sure if this is what you want.


#-------------- Make up a dataset
set.seed(1)
n <- 1e2
DF <- data.frame(year=2010 + sample(3, n, TRUE),
        day=sample(365, n, TRUE),
        val=sample(100, n, TRUE))

a = "day > 100"; b = "val < 50"; c = "year == 2012"
conds <- list(a=a, b=b, c=c)

#-------------- This does it
fun <- function(condition, x){
    f <- function(){}
    if(class(x) == "matrix") x <- data.frame(x)
    if(class(x) == "data.frame")
        body(f) <- with(x, parse(text=condition))
    else
        body(f) <- parse(text=condition)
    f()
}

#-------------- Test the function
year <- DF$year # See if it works with vectors
fun(b, year)    # Must throw error
fun(c, year)    # Should work

# And now with data.frames
result <- lapply(conds, fun, DF)

Reduce(`&`, result) # combine the results
Reduce(`|`, result) #


Hope this helps,

Rui Barradas

Em 02-07-2012 18:04, Christof Klu? escreveu:

Hi

how would you save conditions like

a = "day > 100"; b = "val < 50"; c = "year == 2012"

in a list? I like to have variables like "day", "val", "year" and a list
of conditions list(a,b,c). Then I want to check if a & b & c is true or
if a | b | c is true or similar things.

Greetings
Christof