CODEWITHSUNDEEP
arraysrsubset
T_stats_3
T_stats_3

Reputation: 155

Subsetting an array based on multiple columns

I have a large array in r and would like to subset it using points I obtained from a different matrix.

i.e. 

,,1 
34  1  1  3  4
32  1  3  4  5
23  1  1  3  4
35  1  3  4  4
23  1  2  3  4

,,2 
234  1  1  3  4
32   1  3  4  5
324  1  1  3  4
23   1  3  4  4
232  1  2  3  4

and would like it to return 

34  1  1  3  4
23  1  1  3  4
23  1  2  3  4
234  1  1  3  4
324  1  1  3  4
232  1  2  3  4

in some format.

These particular rows would be returned as I am choosing based on the last 3 columns (i.e I want all the rows with last 3 digits 1,3,4 and 2,3,4)

Upvotes: 0

Views: 117

Answers (1)

akrun
akrun

Reputation: 887078

One way is

m1 <- apply(ar1, 2, `[`)
m1[m1[,2]%in% 1:2 & m1[,3]==3 & m1[,4]==4,]
 #      [,1] [,2] [,3] [,4]
#[1,]    1    1    3    4
#[2,]    1    1    3    4
#[3,]    1    2    3    4
#[4,]    1    1    3    4
#[5,]    1    1    3    4
#[6,]    1    2    3    4

Or

 res <- do.call(rbind,lapply(seq(dim(ar1)[3]), function(i) {
                      x1 <- ar1[,,i]
                      x2 <- t(x1[,-1])
                     x1[colSums(x2==c(1,3,4)|x2==c(2,3,4))==3,]}))

res

#     [,1] [,2] [,3] [,4]
#[1,]    1    1    3    4
#[2,]    1    1    3    4
#[3,]    1    2    3    4
#[4,]    1    1    3    4
#[5,]    1    1    3    4
#[6,]    1    2    3    4

Update

Suppose if the values to match are in a matrix with each row as the matching vector.

 toMatch <- rbind(c(1,3,4), c(2,3,4), c(4,3,2), c(1,9,4))
 indx1 <- apply(toMatch, 1, paste, collapse="")

 res <- do.call(rbind,lapply(seq(dim(ar1)[3]), function(i) {
                       x1 <- ar1[,,i]
                       x1[apply(x1[,-1], 1, paste, collapse='') %in% indx1,]
                                 }))

data

ar1 <- structure(c(1, 1, 1, 1, 1, 1, 3, 1, 3, 2, 3, 4, 3, 4, 3, 4, 5, 
4, 4, 4, 1, 1, 1, 1, 1, 1, 3, 1, 3, 2, 3, 4, 3, 4, 3, 4, 5, 4, 
4, 4), .Dim = c(5L, 4L, 2L))

Upvotes: 1

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