which
Find TRUE Values
Description
Returns a vector of indices identifying the TRUE values of a
logical vector.
Usage
which(x, arr.ind = FALSE, useNames = TRUE)
arrayInd(ind, .dim, .dimnames = NULL, useNames = FALSE)
Arguments
| x |
A logical vector, a matrix, or an array.
|
| arr.ind |
a logical value.
- If FALSE (the default), and x is a matrix or an
array, which returns vector indices of TRUE values of x.
- If TRUE, and x is a matrix or an array, which returns
a length(x) by length(dim(x)) matrix of the row, column, etc. indices
of the TRUE values of x.
See the Value section for more details.
|
| ind |
a numeric or complex value. NAs are allowed.
|
| .dim |
a numeric vector, the length of which is the number column of returned value,
and elements are used as modulo for ind.
|
| .dimnames |
a list of length 2 giving a dimnames attribute for
the matrix. Each component must either have length 0 or
be a vector of character strings with length equal to the
corresponding element of the dim attribute of the result.
|
| useNames |
a logical value. if TRUE, set dimnames attribute for
the returned matrix.
|
Details
if length of .dim is 2, use c("row", "col") as second
element of "dimnames" attribute of returned matrix,
else use dim1, dim2, ... as second element of "dimnames"
attribute of returned matrix.
if length of .dim is no less than 2, modulo of ind
is .dim[i] *.dim[i - 1], else is .dim[1].
Value
| which |
If arr.ind=FALSE, returns the vector indices of the TRUE
values in x, along with the corresponding names, if available, of
x.
If arr.ind=TRUE and x is an array, returns the row, column, etc. indices of the
TRUE values in x. The values are returned in a matrix with one
column for each dimension of the input array, along with the corresponding row
names, if available, of x.
|
| arrayInd |
Returns the same as which(array(x, dim=.dim, dimnames=.dimnames, arr.ind=TRUE, useNames=useNames).
|
See Also
Examples
x <- c(10,20,30,NA,40)
which(x>=30)
x[which(x>=30)]
which( cbind(c(T,F,F), c(F,F,T)), arr.ind=T)
tbl <- array(c(1,7,9,3), dim=c(2,2), dimnames=list(ID=c("A","B"), Attribute=c("Length","Width")))
which(tbl > 5, arr.ind=TRUE)