[R] [FORGED] Merging a dataframe after subsetting with respect to several factors
Rolf Turner
r@turner @end|ng |rom @uck|@nd@@c@nz
Fri Jun 14 01:01:59 CEST 2019
On 14/06/19 5:30 AM, Tina Chatterjee wrote:
> Hello everyone!
> I have the following dataframe(df).
>
> a<-c("a1","a2","a2","a1","a1","a1")
> b<-c("b1","b1","b1","b1","b1","b2")
> c<-c("c1","c1","c1","c1","c1","c2")
> time <- c(runif(6,0,1))
<SNIP>
<rant on>
I know that it's basically harmless, but it drives me nuts when people
do things like:
> time <- c(runif(6,0,1))
What the <expletive deleted> do you think that the c() construction is
doing? ("Hint": Absolutely nothing!!! You get the same result as
you'd get from "time <- runif(6,0,1)" --- or, better, time <- runif(6).
Note that 0 and 1 are the *default* values and *need not be specified*!)
The c() function *catenates* a number of objects (usually vectors)
together. Modulo a certain amount of over-simplification, applying c()
to a single object just returns that object.
(Example of why that's an over-simplification: if m is a matrix,
c(m) strips away the "dim" attribute of m and you just get the vector of
entries of m, strung out in column order. This is however not advised;
see fortunes::fortune("side effects").)
Using c() as you have done indicates that you don't really understand
what you're doing, and that's *not* the way to get the best out of R.
<rant off>
cheers,
Rolf
--
Honorary Research Fellow
Department of Statistics
University of Auckland
Phone: +64-9-373-7599 ext. 88276
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