subsetting matrix with id from another matrix

Question

I would like to subset the data of one matrix using data in a second matrix. The columns of one matrix is labeled. For example,

area1 <- c(9836374,635440,230         


        

Answer 1

split(as.data.frame(mat1), apply(mat2, 1, paste, collapse = " "))
#$`1 2 5`
#       a1     a2      a3
#1 9836374 635440   23018
#3  879042 220539  870581
#4  217418 552303  269359
#5  833696 936079 1472449
#
#$`30 31 34`
#      a1     a2      a3
#2 833696 936079 1472449
#6 879042 220539  870581
#
#$`51 52 55`
#      a1     a2      a3
#7 833696 936079 1472449
#
#$`81 82 85`
#      a1     a2     a3
#8 879042 220539 870581