R help - Nov 2002 - Plotting continuous line types w/large datasets

Hi, R-Folks,

I have 3 large datasets that I combined in a single plot with

plot(ecdf(x1...),...)
plot(ecdf(x2...),add=TRUE,...)
plot(ecdf(x3...),add=TRUE,...)

The datasets are very similar, so it is difficult to get visual
separation among them. I tried many different line types without
success -- the lines all came out solid. Checking further, plot.ecdf()
calls plot.stepfun(), which calls segments() between each pair of
points to plot. Since the points are so close together the lty
parameter becomes meaningless, which is why the lines come out solid.
I modified plot.stepfun() to call lines() for the whole vector of
points, but this didn't seem to help. So my question is: is there a
call I can make to plot a large dataset where the specified line type
gets "continued" through all the points? Or perhaps someone can
suggest
a workaround.

Thanks,
Richard

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liston at cc.gatech.edu (Richard Liston) writes:
> Hi, R-Folks,
> 
> I have 3 large datasets that I combined in a single plot with
> 
> plot(ecdf(x1...),...)
> plot(ecdf(x2...),add=TRUE,...)
> plot(ecdf(x3...),add=TRUE,...)
> 
> The datasets are very similar, so it is difficult to get visual
> separation among them. I tried many different line types without
> success -- the lines all came out solid. Checking further, plot.ecdf()
> calls plot.stepfun(), which calls segments() between each pair of
> points to plot. Since the points are so close together the lty
> parameter becomes meaningless, which is why the lines come out solid.
> I modified plot.stepfun() to call lines() for the whole vector of
> points, but this didn't seem to help. So my question is: is there a
> call I can make to plot a large dataset where the specified line type
> gets "continued" through all the points? Or perhaps someone can
suggest
> a workaround.
Changing the colour might work better.

All the step function plotting seems afflicted by this. Compare

  plot(sort(x),(1:10000)/10000, type="s", lty="dashed")
  plot(sort(x),(1:10000)/10000, type="l", lty="dashed")

The latter might lead to a passable workaround.

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
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~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
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