[R] plot output function

Martin Maechler maechler at stat.math.ethz.ch
Fri May 23 18:31:44 CEST 2003

I guess you forgot that lines(x,y) , contrary to  plot(x,y)
needs  *increasing* (or decreasing) `x' to make sense in your

Hence use something like

fit <- yourcoolfunction(x,y, ...)
ix <- order(x)
lines(x[ix], fit[ix], col = 2)


>>>>> "cp133" == cp133  <cp133 at york.ac.uk>
>>>>>     on Fri, 23 May 2003 17:03:35 +0100 writes:

    cp133> no, I'm afraid abline does not help, it works only
    cp133> for straight lines.  The output of my function is a
    cp133> vector of fitted values (called fit).  I would like
    cp133> to superimpose the fitted regression line to the
    cp133> scatterplot of the data.  Therefore, I use the
    cp133> commands "plot(x,y)"to display the scatterplot; then
    cp133> "lines(x,fit)" to add the estimated regression line.
    cp133> The graph displays the scatterplot correctly but not
    cp133> the fitted regression line.  When I use the command
    cp133> "plot(x,fit)" I get the correct regression line but
    cp133> the plot is very rough, it looks like that, instead
    cp133> of a single clear line, I get several thin lines.

    cp133> Hope this is clearer.

    cp133> Thank you,

    cp133> Chiara

    cp133> Uwe Ligges wrote:
    >>  cp133 wrote: > Hi,
    >> >
    >> > I have written my own function to estimate a local
    >> linear regression.  > When I plot the output vector on
    >> the scatterplot of the data, the > function lines does
    >> not work and I get a rescaled regression line.  > When I
    >> plot the output vector alone, the graph looks right, but
    >> choosing > the type "line" instead of the default does
    >> not deliver a clear single > line.
    >> >
    >> > Does somebody know why this is happening.
    >> >
    >> Does abline() help?
    >> If not, please be more specific in your question and tell
    >> us what you are exactly going to do.
    >> Uwe Ligges

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