I found what's responsible for it but I have no clue what's the origin and
how to solve it.
Apparently it is caused by a special character in the text chunk, the
apostrophe. Like: Ties were handled with Breslow's approximate likelihood.
Then the underscore key does not produce the assignemnt sign in all the
following code chunks. If I removed the apostrophe or if I have a second
apostrophe in the same text chunk, all is ok in the following code chunks.
Encoding problem?

Denis



2012/10/30 Martin Maechler <maechler@stat.math.ethz.ch>

> >>>>> Denis Haine <denis.haine@gmail.com>
> >>>>>     on Mon, 29 Oct 2012 11:26:36 -0400 writes:
>
>     > Hello, After upgrading to emacs 24 (emacs 24.2.1, ess
>     > 12.09) I noticed the underscore key is not mapped anymore
>     > to the R/S assignment sign when into a Rnw buffer. The
>     > underscore key is still correctly giving the assignment
>     > sign when into a R buffer. How can I restore the usual
>     > underscore behavior in a noweb buffer?  Thanks for your
>     > help,
>
> I'm pretty sure this was not a universal problem.
> Our group here uses ESS 12.09 (I'm using the development version),
> and we use Sweave ( *.Rnw ) very very often.
> Nobody has told me about such a problem.
>
> Couldn't it be that it happens exactly in the situation where
> The switch from  R mode ("code chunk")  to  latex mode  ("text chunk")
> does not quite work... and we know that happens not so
> infrequently.  But you can always work around that by "re
> syncing" or sometimes easiest by re-opening the *.Rnw file.
>
> Martin
>
>     > Denis
>
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>

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