get_val {lazy.tools}

R Documentation

Get Values from an Array

Description

Get Values from an Array

Usage

get_val(A, i = NULL, j = NULL, k = NULL, l = NULL, subs = NULL)

put_val(A, i = NULL, j = NULL, k = NULL, l = NULL, subs = NULL) <- value

Arguments

A	An array object
i	Vector consisting of the subscripts for the 1st dimension
j	Vector consisting of the subscripts for the 2nd dimension
k	Vector consisting of the subscripts for the 3rd dimension
l	Vector consisting of the subscripts for the 4th dimension
subs	string specifying the subscripts such as "1:2, , 4, 2:2" or a numeric vector consisting of the scalar subscript for each dim.
value	The value to be assigned.

Details

It is assumed that A is an array.
When A is a list of data frames, use get_valL instead.
When numeric subs is given it must be a vector of length length(dim(A)) specifying a scalar element of A.

get_val(A,i,j,k,l) returns A[i,j,k,l].
put_val(A,i,j,k,l) <- value puts the value at A[i,j,k,l].
Therefore, when A is an array, better use A[i,j,k,l].

get_val(A,i,j,k,l) is equivalent to get_val(A,subs=subs)
where subs contains the values of i,j,k,l as a string.
For example,
get_val(A, 1:2, , 3) is equivalent to get_val(A, subs="1:2, , 3").

Use subs= when the # of dimensions is more than 5.

subs= has priority over i,j,k,l.

The result will be simplified to a matrix or vector if possible.

Value

get_val(A, i,j.,k,l) returns A[i,j,k,l].
put_val(A, i,j,k,l) <- value replaces A[i,j,k,l] with value.

Examples

# set up an array B
dims=c(5,4,3,2)
B <- array(0,dims)
B[,,,1] <- demomat(5,4,3)*10+1
B[,,,2] <- demomat(5,4,3)*10+2
dimnames(B) <-
 mapply( function(x,y){paste(x,1:y,sep="")}, letters[1:length(dims)],dims)

# get B[5,4,3,2]
res1=get_val(B,5,4,3,2)
res2=get_val(B,subs=c(5,4,3,2))
res3=get_val(B,subs="5,4,3,2")
Print(res1,res2,res3)

# get B[2,,3,]:  cannot use numeric subs here.
res1=get_val(B,2,,3)
res3=get_val(B,subs="2,,3,")
Print(res1, res3 )

# modify B[,1,2:3,1]
( temp <- B[,1,2:3,1] )
put_val(B,,1,2:3,1) <- -9999
B[,1,2:3,1]
put_val(B,subs=",1,2:3,1") <- temp
B[,1,2:3,1]
put_val(B,subs=c(1,1,1,2)) <- -9999
B[1,1,1,2]

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