[R] default values

[Ravi Varadhan]

You just need to return the values computed when a==0 and when a!=0.

a=0
f=function(x,y,z=0) {
    if (a==0) return(x[1]+x[2]+y)
    if (a!=0) return(x[1]+x[2]+y+z)
}

> f(1:2,3)
[1] 6
>

Ravi.

----------------------------------------------------------------------------
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Ravi Varadhan, Ph.D.

Assistant Professor, The Center on Aging and Health

Division of Geriatric Medicine and Gerontology 

Johns Hopkins University

Ph: (410) 502-2619

Fax: (410) 614-9625

Email: rvaradhan at jhmi.edu

Webpage:  http://www.jhsph.edu/agingandhealth/People/Faculty/Varadhan.html

 

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-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
Behalf Of Dwayne Blind
Sent: Wednesday, March 12, 2008 1:59 PM
To: r-help at r-project.org
Subject: [R] default values

Dear R users,

I wrote the following toy example to explain my problem :

a=0
f=function(x,y,z) {
    if (a==0) x[1]+x[2]+y
    if (a!=0) x[1]+x[2]+y+z
}
f(1:2,3)


I have not specified z and I get an error. Although a=0, R seems to want to
know z because it's in the expression x[1]+x[2]+y+z.

So I tried to put a default value :

a=0
f=function(x,y,z=0) {
    if (a==0) x[1]+x[2]+y
    if (a!=0) x[1]+x[2]+y+z
}
f(1:2,3)

Why isn't it working ? Sometimes everything is fine even though a parameter
is not specified.

Thanks a lot.

	[[alternative HTML version deleted]]

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