I'm having an issue similar to this old one:
My R View node is very slow, also outside of loops. As explained in post above, when startign the node there is usually a 3 second delay where the node just stays at 0 and then it completes immedialtely. So for me it's clear the issue lies in the interface to R and not R itself (Using R version that ships with knime) due to the delay at the start and the fact that the amount of data and visualizations I create are trivial. In fact I can create a table with 1 row and 1 column and do nothing in the R View Node and these 3 seconds still happen. Probably this is R starting uo taking so long?
I tired it on 2 different PCs and the behavior is the same:
Windows Server 2012 R2 with 32 Gb of RAM
Windows 7 with 8 GB of RAM.
So it's either a KNIME issue or Windows issue.