# SCM Repository

[matrix] Diff of /pkg/TODO
 [matrix] / pkg / TODO

# Diff of /pkg/TODO

revision 1887, Thu Jun 7 09:04:34 2007 UTC revision 2043, Sat Aug 11 03:18:26 2007 UTC
# Line 142  Line 142
142    !M  where M is "sparseMatrix", currently always gives dense. This only    !M  where M is "sparseMatrix", currently always gives dense. This only
143    makes sense when M is ``really sparse''.    makes sense when M is ``really sparse''.
144
145  - column names of sparse matrices are not printed;  - log1p(<sparseMatrix>) "should" give <dsparseMatrix>
146    we now "mention" them (if they are non-empty).    Pretty surely, this would happen automagically, if "log1p" became part of
147    Option:    "Math" group generic ---> which is the case from R 2.6.0 on
build show( <sparseMatrix>) on a function, possibly
print.sparseMatrix(), which gets an argument such as
'col.names.show  = FALSE' which is documented and can be set to TRUE
148
149  - 'arules' needs fast colSums() and rowSums() - for ngCMatrix;  - msy <- as(matrix(c(2:1,1:2),2), "dsyMatrix"); str(msy)
150    do it for "nMatrix" and "lMatrix" and return *integer*
151      shows that the Cholesky factorization is computed ``too quickly''.
152      Can be a big pain for largish matrices, when it is unneeded.
153
154    - example(Cholesky, echo=FALSE) ; cm <- chol(mtm); str(cm); str(mtm)
155
156      shows that chol() does not seems to make use of an already
157      present factorization and rather uses one with more '0' in x slot.
158
159    - diag(m) <- val    currently automatically works via  m[cbind(i,i)] <- val
160      However,
161      we need methods for 'diag<-' at least for diagonalMatrix,
162      triangularMatrix, and probably also "dense*general*Matrix" since the
163      above currently goes via "matrix" and back instead of using the 'x' slot
164      directly.
165
166    - image(M, aspect= "iso", colorkey = FALSE)
167      really should be default; {aspect: non-back comptible for users !!}
168      current default colorkey=TRUE is on abs(M[M > 0]).
169      Note: Think about an optional smart option which keeps "0 |-> transparent"
170      but allows colors to differentiate negative and positive entries.
171      --- and be documented! Maybe move from man/dgTMatrix-class.Rd to image.Rd ?
172
173    - examples for solve( Cholesky(.), b, system = c("A", "LDLt"....))
174      probably rather in man/CHMfactor-class.Rd than man/Cholesky.Rd

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