On 18/01/10 16:47, Luca Beltrame wrote:
Hello,
I'm porting over some code from pure R to RPy2.1 (because I'm using R only to
perform the calculations, as I much prefer the data in other structures that
are more efficient) and I stumbled upon a function (which I didn't originally
write) that uses "which".
As far as I can remember, there isn't a perfect equivalent in Python: the
alternative would be using "which" with "robjects.r("expressiongoeshere")" but
as the object is created "outside" I would like to avoid that.
The "offending" code is (in R):
length(which(keys == mydata$label))
(mydata is a R list - hence I would be able to use the .rx2 accessor)
Has anyone got a hint on how to translate this using rpy 2.1.x?
There are many ways. For example:
# translation of the R code into rpy2
from rpy2.robjects.packages import importr
base = importr("base")
eq = base.__dict__["=="]
which = base.which
len(which(eq(keys, mydata.rx("label"))))
# A more "Pythonic" way would be
# (although with an overhead as each element in the
# column "label" will be converted into a Python
# object before comparison)
len([i+1 for i, x in enumerate(mydata.rx("label")) if x == keys])
L.
Thanks!
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world's best and brightest in the field, creating opportunities for Conference
attendees to learn about information security's most important issues through
interactions with peers, luminaries and emerging and established companies.
http://p.sf.net/sfu/rsaconf-dev2dev
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