[R] why won't rq draw lines?

[david_foreman@doctors.org.uk]

Thanks, this works for me as well, though the lines extend beyond the Y axes (sometimes).  I'm very grateful.  

---------- Original Message ----------------------------------
From: "Liaw, Andy" <andy_liaw at merck.com>
Date:  Mon, 19 Jul 2004 10:04:55 -0400

>This works for me:
>
>data(engel)
>plot(engel$x, engel$y, xlab="household income", ylab="food expenditure",
>     cex=.5)
>taus <- c(.05,.1,.25,.75,.9,.95)
>lapply(taus, function(tau) abline(coef(rq(y~x, data=engel, tau=tau))))
>
>HTH,
>Andy
>
>> -----Original Message-----
>> From: r-help-bounces at stat.math.ethz.ch
>> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of
>> david_foreman at doctors.org.uk
>> Sent: Monday, July 19, 2004 9:53 AM
>> To: r-help at stat.math.ethz.ch
>> Subject: [R] why won't rq draw lines?
>>
>>
>> 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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>
>
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