problems creating data frames

I am having two problems creating data frames that I have solutions, but
they really seem like kludges and I assume I just don't understand the
proper R way of doing things.

The first situation is I have an set of uneven data vectors. When I try to
use them to create a data frame I would like the bottoms of them padded with
NAs, without explicitly specifying that. When I do:

anxiety.data = data.frame(Behavior_Therapy = c(6, 7, 6, 5, 5, 5, 7, 8, 9, 6,
6, 7),
                         Atenolol = c(4, 8, 10, 3, 6, 5, 6, 3, 7, 5, 4, 6),
                         Placebo = c(0, 7, 0, 7, 0, 7))

It duplicates the values for Placebo twice. I can correct this by doing:

anxiety.data = data.frame(Behavior_Therapy = c(6, 7, 6, 5, 5, 5, 7, 8, 9, 6,
6, 7),
                         Atenolol = c(4, 8, 10, 3, 6, 5, 6, 3, 7, 5, 4, 6),
                         Placebo = c(c(0, 7, 0, 7, 0, 7), rep(NA, 6)))

But this requires me to look at the length of the vectors and explicitly pad
them. Is there a method to say, "create a data frame and any vectors that
are too short should be padded with NAs"?

My second situation has to do with the names of columns. When I do:

rat.data = data.frame("S+/P+" = c(25,23,18,16,12,19,20,21),
                     "S+/P-" = c(18,17,16,11,14,15,21,12),
                     "S-/P+" = c(20,12,15,13,8,17,17,18),
                     "S-/P-" = c(12,15,17,10,18,10,9,14))

I end up with the column names: S..P., S..P..1, S..P..2, and S..P..3. If I
rename them using:

names(rat.data) = c("S+/P+", "S+/P-", "S-/P+", "S-/P-")

Then I get them named what I attempted to name them initially. Is there some
way to just have them named what I attempted to name them in the first
place? I don't really know why they're being renamed since the names are
valid, so I'm not really sure what to try to find to correct the naming.

Will

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