R help - Jul 2005 - question for IF ELSE usage

Hi R users,
 Maybe the question is too simple.
 In a IF ... ELSE ... statement "if(cond) cons.expr else alt.expr", IF
and
ELSE should be at the same line? 
For example,
 if (x1==12)
{
y1 <- 5 
}else
{
y1 <- 3
}
 is right, while
 if (x1==12)
{
y1 <- 5 
}
else # Error: syntax error
{
y1 <- 3
}
 is wrong? 
 Thanks

-- 
Xiaohua Dai
--------------------------------------------------------------------------------
Centre for Systems Research, Durban Institute of Technology
P.O.Box 953, Durban 4000, South Africa
Tel: +27-31-2042737(O) Fax: +27-31-2042736(O)
Mobile: +27-723682954

	[[alternative HTML version deleted]]

On Tue, 2005-07-12 at 16:22 +0200, ecoinfo wrote:
> Hi R users,
>  Maybe the question is too simple.
>  In a IF ... ELSE ... statement "if(cond) cons.expr else
alt.expr", IF and
> ELSE should be at the same line? 
> For example,
>  if (x1==12)
> {
> y1 <- 5 
> }else
> {
> y1 <- 3
> }
>  is right, while
>  if (x1==12)
> {
> y1 <- 5 
> }
> else # Error: syntax error
> {
> y1 <- 3
> }
>  is wrong? 
>  Thanks
Note the following from the Details section of ?"if"

"Note that it is a common mistake to forget to put braces ({ .. })
around your statements, e.g., after if(..) or for(....). In particular,
you should not have a newline between } and else to avoid a syntax error
in entering a if ... else construct at the keyboard or via source. For
that reason, one (somewhat extreme) attitude of defensive programming is
to always use braces, e.g., for if clauses."


One other approach is the following:

if (x1 == 12) 
{
  y1 <- 5 
} else {
  y1 <- 3
}

Note the presence of both braces on the 'else' line.

HTH,

Marc Schwartz