On Sep 5, 2006, at 5:54 PM, Thomas Lumley wrote: > The problem in >> D = list(ABCD=2:1) >> D$ABC[]<-3:4 >> D > $ABCD > [1] 3 4 > > $ABC > [1] 3 4 > > is that eval.c:evalseq ends up with a reference to D$ABCD from > evaluating D$ABC with partial matching. Since evalseq doesn't (and > shouldn't) increase NAMED on these partially evaluated calls, NAMED > is still 1 for D$ABCD. When evalseq's D$ABC has 3:4 assigned into > it the vector is changed directly, since NAMED=1, and both D$ABC > and D$ABCD change.
This problem does not appear when the following is done > D = list(ABCD=2:1) > D$ABC[]=c(3,4) > D $ABCD [1] 2 1 $ABC [1] 3 4 Or when this is done: > D = list(ABCD=2:1) > D[["ABC"]][]=3:4 > D $ABCD [1] 2 1 $ABC [1] 3 4 But it does appear when the following is done: > D = list(ABCD=2:1) > X = 3:4 > D$ABC[]=X > D $ABCD [1] 3 4 $ABC [1] 3 4 But not when the following is done: > D = list(ABCD=2:1) > X = 3:4 > X[1] = 1 > D$ABC[]=X > D $ABCD [1] 2 1 $ABC [1] 1 4 It appears to be a sequence specific bug for the $ operator, which might explain why it did not occur with my original examples where I had a character data column, but did appear where I had a numeric data column that was a sequence. Going back to the original partial replacement problem, is there anyway to turn off partial matching, or to selectively apply exact matching when trying to access a single element? I can get the desired single element match using the convoluted syntax D["ABC"] [[1]] and perform partial replacement operations on a new column. However, it would be nice to have single element access operator that does exact matching. Anil ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
