dplyr and function length() and some apologies

Dear Hadley:

your request for evidence for my observation seems to have paved the way 
to solve this issue. As it turns out, the effect I described only occurs 
with "data.frames" read in with readxl. Clearly, I missed that these are 
tbl_df. And that explains the differential behavior depending on whether 
dplyr is loaded or not. Also, I realize that this latter effect can be 
avoided by explicitly converting objects read in with readxl to a 
data.frame.

Well, I should have known that if i had carefully read the README stuff 
for readxl. But then, readxl is so much of an every-day tool for me that 
I didn't even think of its involvement in my problem, all the more as 
the reference manual does not mention the format/class of objects read 
in with readxl.

So my apologies for any confusion I may have caused - and I certainly 
did not mean my observation as a charge against dplyr or its authors. 
Quite to the contrary, i appreciate thees tools, and as you may see, 
tray to understand and use them.

Thank you so much again

Karl

No, the effect I described has nothing to do wit USING dplyr. It occurs with

any (preexisting) data.frame once dplyr is LOADED (require(dplyr). It is
this silent, sort of "backward acting" effect that disturbs me.

You're going to need to provide some evidence for that charge: dplyr
does not affect the behaviour of data.frames (only tbl_dfs)

Hadley

Karl Schilling