# [R] vectorising ifelse()

Kevin Bartz bartzk at yahoo-inc.com
Fri Jul 22 03:14:03 CEST 2005

```The code as you provided it is a bit unusual. In the second assignment,
you're using "drow[i]>0" as an index into "new," but ifelse has already
found that condition to be true, which means what you wrote is just the
same as saying new[1,zappo[i]].

Also, if zappo and zappo are vectors of probabilities, why are they
being used as indices into new? Indices are supposed to be integers or
T/Fs.

It would be nice if you could provide some example data. I'm sure
there's a way to vectorize it, but I'm struggling to get my head around
the Zippos, zappos and haplos.

Kevin

-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Federico Calboli
Sent: Thursday, July 21, 2005 4:44 PM
To: r-help
Subject: [R] vectorising ifelse()

Hi All,

is there any chance of vectorising the two ifelse() statements in the
following code:

for(i in gp){
new[i,1] = ifelse(srow[i]>0, new[srow[i],zippo[i]], sample(1:100, 1,
prob =Y1, rep = T))
new[i,2] = ifelse(drow[i]>0, new[drow[i]>0,zappo[i]], sample(1:100,
1, prob =Y1, rep = T))
}

Where I am forced to check if the value of drow and srow are >0 for each
line... in practical terms, I am attributing haplotypes to a pedigree,
so I have to give the haplotypes to the parents before I give them to
the offspring. The vectors *zippo* and *zappo* are the chances of
getting one or the other hap from the sire and dam respectively. *gp* is
the vectors of non-ancestral animals. *new* is a two col matrix where
the haps are stored.

Cheers,

Federico

--
Federico C. F. Calboli
Department of Epidemiology and Public Health
Imperial College, St Mary's Campus
Norfolk Place, London W2 1PG

Tel  +44 (0)20 7594 1602     Fax (+44) 020 7594 3193

f.calboli [.a.t] imperial.ac.uk
f.calboli [.a.t] gmail.com

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