What i want to have is a matrix in which each element is a list itself. See the following example:
1 2 3
1 1,2,4 1,2 1
2 Null 3,4,5,6 1,3
I saw this post, and tried the following but got an error :
b <- array()
b[j, i, ] <- A[i]
where A is a vector itself. The error was:
Error in b[j, i, ] <- A[i] : incorrect number of subscripts
How should I define and access each element of the matrix and each element of the contained lists?
Update1 :
b<-matrix(list(),nrow = length(d), ncol =length(c))
Error in b[j, i] <- A[i] : replacement has length zero
I want to specify that each element is a list and then try to fill it with various list with different length from zero to n.
Update2 :
running what @BondedDust commented :
b<-matrix(rep(list(),(c*d)),,nrow = length(d), ncol =length(c))
Erorr in b[[j*nrow(b)+i]] <- A[i] : attempt to select less than one element
A :
A[1]<-c(3) F[[1]]<-numeric(0) E[[1]]<-numeric(0)
A[2]<-c(1) F[2]<-c(1) E[2]<-c(1)
A[3]<-c(1) F[3]<-c(2) E[[3]]<-numeric(0)
A[[4]]<-c(1,3) F[[4]]<-numeric(0) E[[4]]<-numeric(0)
A[5]<-c(4) F[5]<-c(4) E[5]<-c(4)
A :values of row 1 , F:row 2 and E :row 3. ( 5 column )
this data is not in this form and is not stored any where,they are the output of another function (there is function in the place of A[i]
).the data just show what dose A
look likes reproducibly and therefore shows the position in the matrix and gives back the error
in update2.A[4]
is the element of column 4 row 2.
This builds that matrix although the print method does not display it in the manner you imagined:
matrix( list(c(1,2,4), c(NULL), c(1,2), c(3,4,5,6), c(1), c(1,3)), 2,3)
#---------
[,1] [,2] [,3]
[1,] Numeric,3 Numeric,2 1
[2,] NULL Numeric,4 Numeric,2
Inspect the first element:
> Mlist <- matrix( list(c(1,2,4), c(NULL), c(1,2), c(3,4,5,6), c(1), c(1,3)), 2,3)
> Mlist[1,1]
[[1]]
[1] 1 2 4
> is.matrix(Mlist)
[1] TRUE
> class( Mlist[1,1] )
[1] "list"
Demonstration of creating "matrix of lists" from a list:
> will.become.a.matrix <- list(c(1,2,4), c(NULL), c(1,2), c(3,4,5,6), c(1), c(1,3))
> is.matrix(will.become.a.matrix)
[1] FALSE
> dim(will.become.a.matrix) <- c(2,3)
> is.matrix(will.become.a.matrix)
[1] TRUE
> dim(will.become.a.matrix)
[1] 2 3
> class(will.become.a.matrix[1,1])
[1] "list"
Further requested demonstration:
A<- list(); F=list() E=list()
A[1]<-c(3) ; F[[1]]<-numeric(0); E[[1]]<-numeric(0)
A[2]<-c(1) ; F[2]<-c(1) ; E[2]<-c(1)
A[3]<-c(1) ; F[3]<-c(2) ; E[[3]]<-numeric(0)
A[[4]]<-list(1,3) ;F[[4]]<-numeric(0) ; E[[4]]<-numeric(0)
A[5]<-c(4) ; F[5]<-c(4) ; E[5]<-c(4)
Mlist= c(A,F,E)
M <- matrix(Mlist, length(A), 3)
#=====================================
> M
[,1] [,2] [,3]
[1,] 3 Numeric,0 Numeric,0
[2,] 1 1 1
[3,] 1 2 Numeric,0
[4,] List,2 Numeric,0 Numeric,0
[5,] 4 4 4
You asked (in comments) "....is there a way to define number of column and rows , but not the element itself because they are unknown?"
Answered (initially in comments)
b<-matrix(rep(list(), 6),nrow = 2, ncol =3)
#.... then replace the NULL items with values.
# Need to use "[[": for assignment (which your 'Update 1' did not
# ....and your Update2 only did for some but not all of the assignments.)
b[[1]] <- c(1,2,3,4)
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