I realize that you can break this approach as well with a suitably complex
expression, but I took it as a challenge:
> dat <- data.frame(ASB = c(LETTERS[1:3]), Flow=c(11.51, 9.2, 10.5),
> stringsAsFactors=FALSE)
> cat <- LETTERS[1:3]
> mult <- c("'*'(2," , "'+'(5,", "sqrt(")
> sapply(parse(text=paste0(mult[match(dat$ASB, cat)], dat$Flow, ")")), eval)
[1] 23.02000 14.20000 3.24037
David
-----Original Message-----
From: Bert Gunter [mailto:bgunter.4...@gmail.com]
Sent: Tuesday, September 15, 2015 4:43 PM
To: David L Carlson <dcarl...@tamu.edu>
Cc: Peter Alspach <peter.alsp...@plantandfood.co.nz>; r-help@r-project.org
Subject: Re: [R] Multiple if function
Thanks, David.
I would say, not quite.
What if the alternatives are:
If class = "a" multiply y by 2;
If class = "b" add 5 to y;
If class = "c" take sqrt(y)
(where y is numeric, say)
?
Cheers,
Bert
Bert Gunter
"Data is not information. Information is not knowledge. And knowledge
is certainly not wisdom."
-- Clifford Stoll
On Tue, Sep 15, 2015 at 2:11 PM, David L Carlson <dcarl...@tamu.edu> wrote:
> You could use match() and avoid ifelse():
>
>> dat <- data.frame(ASB = c(LETTERS[1:3]), Flow=c(11.51, 9.2, 10.5),
>> stringsAsFactors=FALSE)
>> cat <- LETTERS[1:3]
>> mult <- c(.1, .15, .2)
>> dat$Flow * mult[match(dat$ASB, cat)]
> [1] 1.151 1.380 2.100
>
> -------------------------------------
> David L Carlson
> Department of Anthropology
> Texas A&M University
> College Station, TX 77840-4352
>
>
> -----Original Message-----
> From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Bert Gunter
> Sent: Tuesday, September 15, 2015 3:51 PM
> To: Peter Alspach
> Cc: r-help@r-project.org
> Subject: Re: [R] Multiple if function
>
> ... but this only works if ASBclass is numeric. What if it is a factor
> (or even character)?
>
> One can always finesse factors in simple cases like this, but for 2
> reasons, I don't think it's a good idea.
>
> 1. One should make use of a factor's API, rather than its internal
> integer representation(which, I grant, ain't likely to change);
>
> 2. For more complicated alternatives (e.g. entirely different
> functions depending on the factor value) it won't work anyway.
>
> For simple cases, ifelse() seems reasonable; but for more alternatives
> -- say 10 or 50 -- this becomes too cumbersome (imho). I think the
> split and recombine approach then becomes the best option, but maybe
> there is some easier, shorter, approach that I am overlooking. Please
> correct me if this is the case.
>
> Best,
> Bert
>
>
>
>
>
>
> Bert Gunter
>
> "Data is not information. Information is not knowledge. And knowledge
> is certainly not wisdom."
> -- Clifford Stoll
>
>
> On Tue, Sep 15, 2015 at 12:23 PM, Peter Alspach
> <peter.alsp...@plantandfood.co.nz> wrote:
>> Tena koe Maria
>>
>> It seems you need to multiply Flow by 0.05+ASBClass/20 (i.e., no if calls
>> are necessary)
>>
>> HTH ....
>>
>> Peter Alspach
>>
>> -----Original Message-----
>> From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Maria
>> Lathouri
>> Sent: Tuesday, 15 September 2015 10:57 p.m.
>> To: r-help@r-project.org
>> Subject: [R] Multiple if function
>>
>> Dear all,
>>
>> I am writing as I would like your help. I have a dataframe with two columns,
>> ASB and Flow, where the the first one has values 1, 2 or 3 and the second
>> flow data. Something like that:
>> ASBclass Flow1 11.51 9.2
>> 2 10.5
>> 3 6.7 ... ...
>> I would like to produce a third column named eg. deviation where it would
>> get me values based on if ASBclass is 1, multiply Flow by 0.1; if ASBclass
>> is 2 then multiply Flow by 0.15 and if ASBclass is 3 then multiply by 0.2.
>>
>> If (ASBclass=1) { deviation<-Flow*0.1}
>> If (ASBclass=2) { deviation<-Flow*0.15}If (ASBclass=1) {
>> deviation<-Flow*0.2} I am not sure whether I should add the else function
>> and how can I combine these separate functions.
>>
>> Can anyone help me on that?
>> Thank you very much.
>>
>> Kind regardsMaria
>>
>> [[alternative HTML version deleted]]
>>
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