My package 'lsmeans' is now suddenly broken because of a new provision in the
'tibble' package (loaded by 'dplyr' 0.5.0), whereby the "[[" and "$" methods
for 'tbl_df' objects - as documented - throw an error if a variable is not
found.
The problem is that my code uses tests like this:
if (is.null (x$var)) {...}
to see whether 'x' has a variable 'var'. Obviously, I can work around this using
if (!("var" %in% names(x))) {...}
but (a) I like the first version better, in terms of the code being
understandable; and (b) isn't there a long history whereby we can expect a NULL
result when accessing an absent member of a list (and hence a data.frame)? (c)
the code base for 'lsmeans' has about 50 instances of such tests.
Anyway, I wonder if a lot of other package developers test for absent variables
in that first way; if so, they too are in for a rude awakening if their users
provide a tbl_df instead of a data.frame. And what is considered the best
practice for testing absence of a list member? Apparently, not either of the
above; and because of (c), I want to do these many tedious corrections only
once.
Thanks for any light you can shed.
Russ
Russell V. Lenth - Professor Emeritus
Department of Statistics and Actuarial Science
The University of Iowa - Iowa City, IA 52242 USA
Voice (319)335-0712 (Dept. office) - FAX (319)335-3017
Just because you have numbers, that doesn't necessarily mean you have data.
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