Steve,
You're absolutely right that DT[, a := a * 2] is easier to read, but
that's not my point.
Maybe I have not pointed this out clearly enough and I'm sorry about
that, but my point is NOT how to multiply a number by two.
Instead, my point is how to do some calculation with a variable and then
reassign that result back to that variable. (That's the whole rationale
behind `%<>%` in magrittr!)
This calculation could IN REALITY be of course more complicated than *2,
and could involve many functions chained together and a long variable
name that is cumbersome to read/type repeatedly, e.g.
DT[, long.variable.name := long.variable.name %>% function.a %>% function.b]
I do think that the other version would be more easy to read and type:
DT[, long.variable.name %<>% function.a %>% function.b]
Hope that clarifies.
M
On 07/01/2015 04:06 AM, Steve Lianoglou wrote:
Hi,
I love data.table and I also love magrittr.
I really love both of these, too.
However, some things don't work,
e.g.
DT <- data.table(a = 1:3, b = 4:6)
DT[, a %<>% `*`(2)] # instead of DT[, a := a %>% `*`(2)]
In my personal opinion, though, I feel like this might be going a
stretch too far.
Although this might just be a contrived example, it's hard for me to
divine an instance where this would look any less contrived. I mean,
is:
DT[, a %<>% `*`(2)] ## or
DT[, a := a %>% `*`(2)]
Really any more useful/simpler than:
DT[, a := a * 2]
Can't think of when I'd prefer the magrittr'ized version ... perhaps
when the column name (`a`) is actually a much longer? (so that %<>%
saves you some typing), or?
-steve
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