logical operator TRUE/FALSE in R - r

Question

I wrote a simple function that produces all combinations of the input (a vector). Here the input vector is basically a sequence of 4 coordinates (x, y) as mentioned inside the function as a, b,c, and d.
intervals<-function(x1,y1,x2,y2,x3,y3,x4,y4){
a<-c(x1,y1)
b<-c(x2,y2)
c<-c(x3,y3)
d<-c(x4,y4)
union<-expand.grid(a,b,c,d)
union
}
intervals(2,10,3,90,6,50,82,7)
> intervals(2,10,3,90,6,50,82,7)
Var1 Var2 Var3 Var4
1 2 3 6 82
2 10 3 6 82
3 2 90 6 82
4 10 90 6 82
5 2 3 50 82
6 10 3 50 82
7 2 90 50 82
8 10 90 50 82
9 2 3 6 7
10 10 3 6 7
11 2 90 6 7
12 10 90 6 7
13 2 3 50 7
14 10 3 50 7
15 2 90 50 7
16 10 90 50 7
>
Now I want to find (max of x) and (min of y) for each row of the given output. E.g. row 2: we have 4 values (10, 3, 6, 82). Here (3,6,82) are from x (x2,x3,x4) and 10 is basically from y (y1). Thus max of x is 82, and the min of y is 10.
So what I want is two values from each row.
I do not actually know how to approach this kind of logical command. Any idea or suggestions?

Answer 1

You can pass x and y vector separately to the function. Use expand.grid to create all combinations of the vector and get max of x and min of y from each row.
intervals<-function(x, y){
tmp <- do.call(expand.grid, rbind.data.frame(x, y))
names(tmp) <- paste0('col', seq_along(tmp))
result <- t(apply(tmp, 1, function(p) {
suppressWarnings(c(max(p[p %in% x]), min(p[p %in% y])))
}))
result[is.infinite(result)] <- NA
result <- as.data.frame(result)
names(result) <- c('max_x', 'min_x')
result
}
intervals(c(2,3,6,82), c(10, 90, 50, 7))
# max_x min_x
#1 82 NA
#2 82 10
#3 82 90
#4 82 10
#5 82 50
#6 82 10
#7 82 50
#8 82 10
#9 6 7
#10 6 7
#11 6 7
#12 6 7
#13 3 7
#14 3 7
#15 2 7
#16 NA 7