如何基于R中的匹配值将值列表插入到更大的列中

Question

if I have a preallocated array ie"

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

A  

B

C

D

E

F

..

..

Z

how can I insert lists of differing but shorter lengths ie (B,D,E,F) or (A,C,EG,J,K) in to the columns [2] : [6] ?

Thanks,

Answer 1

sapply(newarray, function(elem) { master_list[,2] <- rbind(master_list[,2], elem})

elem is the parameter to the anonymous function, passed as the second argument to sapply . Look in the help for more details.

Answer 2

My rationale for these sorts of problems is to reduce everything to a single assignment. In the case of matrices, you can index them using another matrix to achieve this, like so:

Set up a test array and vectors:

arr <- matrix(NA,nrow=5,ncol=6)
arr[,1] <- LETTERS[1:5]
vec1 <- c("B","D","E")
vec2 <- c("A","C","E","G")

#     [,1] [,2] [,3] [,4] [,5] [,6]
#[1,] "A"  NA   NA   NA   NA   NA  
#[2,] "B"  NA   NA   NA   NA   NA  
#[3,] "C"  NA   NA   NA   NA   NA  
#[4,] "D"  NA   NA   NA   NA   NA  
#[5,] "E"  NA   NA   NA   NA   NA 

Figure out matrix columns to assign to:

vecs <- list(vec1,vec2)
lens <- sapply(vecs,length)
mat <- cbind(sequence(lens),rep(2:3,lens))
mat

#     row   col    
#     [,1] [,2]
#[1,]    1    2
#[2,]    2    2
#[3,]    3    2
#[4,]    1    3
#[5,]    2    3
#[6,]    3    3
#[7,]    4    3

Assign away:

arr[mat] <- unlist(vecs)
arr
#     [,1] [,2] [,3] [,4] [,5] [,6]
#[1,] "A"  "B"  "A"  NA   NA   NA  
#[2,] "B"  "D"  "C"  NA   NA   NA  
#[3,] "C"  "E"  "E"  NA   NA   NA  
#[4,] "D"  NA   "G"  NA   NA   NA  
#[5,] "E"  NA   NA   NA   NA   NA