[R] why won't rq draw lines?

Adaikalavan Ramasamy ramasamy at cancer.org.uk
Mon Jul 19 16:22:24 CEST 2004

The example in help(rq) works for me. 

I presume the problem is not due to attach(forrq) as you get the
scatterplot. Why don't you try printing 'xx' and 'yy' inside the loop
and see what you get.

On Mon, 2004-07-19 at 14:53, david_foreman at doctors.org.uk wrote:
> I've been trying to draw quantile linear regression lines across a scatterplot of my data using 
> attach(forrq)
>      plot(PREGNANT,DAY8,xlab="pregnant EPDS",ylab="postnatal EPDS",cex=.5)
>      taus <- c(.05,.1,.25,.75,.9,.95)
>      xx <- seq(min(PREGNANT),max(PREGNANT),100)
>      for(tau in taus){
>              f <- coef(rq(DAY8~PREGNANT,tau=tau))
>              yy <- (f[1]+f[2]*xx)
>              lines(xx,yy)
>              }
> which is simply the method from the help file with my dataset attached, and the variable names substituted where appropriate.  I get the scatterplot, but no lines.  Any ideas about what's going on? or wrong?
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