
Data Technologies 259
> nullf = function(x, ...) NULL
> yeast2 = xmlTreeParse(Yeastfn,
handlers = list(sequence = nullf,
organism = nullf, primaryRef = nullf,
secondaryRef = nullf,
names = nullf), asTree=TRUE)
We can easily compare the size of the two documents and see that the
second is much smaller.
> object.size(yeastIntAct)
[1] 47253568
> object.size(yeast2)
[1] 11793648
If instead, it is desirable to obtain the entire tree so that it can later be ma-
nipulated and queried, it may be beneficial to set the argument
useInternalNodes to TRUE. This causes the document to be stored in an inter-
nal, to the XML package, format rather than to convert it into