[R] if function problems

[David Winsemius]

On Aug 1, 2011, at 6:57 PM, zoe_zhang wrote:

> Dear All,
> Sorry to bother
> I want to write a function in R using if
> Say I have a dataset x,
> if x[i]<0, then x[i]=x[i],
> if x[i]>0, then x[i]=0
>
> for example, x=-3:3,
> then using the function, x becomes [-3,-2,-1,0,0,0,0]
Just use logical indexing

x[ x>0 ] <- 0

>
> I write the codes as follows,
>
> gjr=function(x)
> {lena=length(x)
> for(i in 1:lenx)
> if (x[i]<0) return (x[i])
> if (x[i]>0) return (0)
> x}
>
> but then, doing
> gjr(x）
> it only comes out with one number

'if' is not the right function. Look at

?"if"
?ifelse

(But the logical indexing is easier in this case than using ifelse.)

-- 
David Winsemius, MD
West Hartford, CT