R help - Jul 2012 - save conditions in a list

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

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
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

Christof,

This isn't quite what you asked for, but perhaps you will find it useful.
You could save the conditions by putting them in a function.
Then you could apply that function to any data frame with the reference 
variables.

For example,

check.conditions <- function(df) {
        cbind(a=df$day > 100, b=df$val < 50, c=df$year==2012)
        }

mydf <- data.frame(day=c(20, 50, 100, 70, 80, 130), val=c(1, 7, 70, 20, 
55, 30), year=2011:2016)

check.conditions(mydf)

         a     b     c
[1,] FALSE  TRUE FALSE
[2,] FALSE  TRUE  TRUE
[3,] FALSE FALSE FALSE
[4,] FALSE  TRUE FALSE
[5,] FALSE FALSE FALSE
[6,]  TRUE  TRUE FALSE

Jean



Christof Kluß <ckluss@email.uni-kiel.de> wrote on 07/02/2012 12:04:40 PM:
> 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
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