[R] Knitr: setting echo = FALSE globally

[Rich Shepard]

   Near the beginning of a LyX document I have a knitr chunk with options
that begin with 'global_options', and includes echo=F. This presents the R
code in that chunk from displaying in the compiled PDF file. However, all
following knitr chunks are included in the PDF file.

   Reading the docs (including the Knitr book) does not show me what I am
doing incorrectly. A pointer to the solution is needed.

Rich