[R] Multiple if function
bgunter.4567 at gmail.com
Wed Sep 16 23:17:43 CEST 2015
I assume it's to return the vectors in their original order.
"Data is not information. Information is not knowledge. And knowledge
is certainly not wisdom."
-- Clifford Stoll
On Wed, Sep 16, 2015 at 2:10 PM, David Winsemius <dwinsemius at comcast.net> wrote:
> On Sep 15, 2015, at 7:20 PM, Charles C. Berry wrote:
>> On Tue, 15 Sep 2015, Bert Gunter wrote:
>>> Thanks to both Davids.
>>> I realize that these things are often a matter of aesthetics -- and
>>> hence have little rational justification -- but I agree with The Other
>>> David: eval(parse) seems to me to violate R's soul( it makes R a macro
>>> language instead of a functional one).
>>> However, mapply(... switch) effectively loops through the frame row by
>>> row. Aesthetically, I like it; but it seems inefficient. If there are
>>> e.g. 1e6 rows in say 10 categories, I think Jeff's approach should do
>>> much better. I'll try to generate some actual data to see unless
>>> someone else beats me to it.
>> Use mapply like this on large problems:
>> function(x,z) eval( x, list( y=z )),
>> expression( A=y*2, B=y+3, C=sqrt(y) ),
>> split( dat$Flow, dat$ASB ),
> Seems unnecessarily complex, but definitely elegant. Was there a reason it was not just:
> function(x,z) eval( x, list( y=z )),
> expression(A= y*2, B=y+3, C=sqrt(y) ),
> split( dat$Flow, dat$ASB )
> Also readers should note that the names in that expression vector are quite arbitrary at the moment. The only association is via the order. I don't suppose someone wants to take on the challenge of matching the names of the expression vector with the names of returned split components?
> David Winsemius
> Alameda, CA, USA
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