| uniquecombs {crs} | R Documentation |
Find the unique rows in a matrix
Description
This routine returns a matrix containing all the unique rows of the matrix supplied as its argument. That is, all the duplicate rows are stripped out. Note that the ordering of the rows on exit is not the same as on entry. It also returns an index attribute for relating the result back to the original matrix.
Usage
uniquecombs(x)
Arguments
x |
is an R matrix (numeric) |
Details
Models with more parameters than unique combinations of covariates are not identifiable. This routine provides a means of evaluating the number of unique combinations of covariates in a model. The routine calls compiled C code.
Value
A matrix consisting of the unique rows of x (in arbitrary order).
The matrix has an "index" attribute. index[i] gives the row of the returned
matrix that contains row i of the original matrix.
Author(s)
Simon N. Wood simon.wood@r-project.org
See Also
unique can do the same thing, including for
non-numeric matrices, but more slowly and without returning the
index.
Examples
X<-matrix(c(1,2,3,1,2,3,4,5,6,1,3,2,4,5,6,1,1,1),6,3,byrow=TRUE)
print(X)
Xu <- uniquecombs(X);Xu
ind <- attr(Xu,"index")
## find the value for row 3 of the original from Xu
Xu[ind[3],];X[3,]