Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of e-letter
> Sent: Thursday, January 08, 2009 9:22 AM
> To: r-help at r-project.org
> Subject: [R] interpolation to abscissa
>
> Readers,
>
> I have looked at various documents hosted on the web site; I couldn't
> find anything on interpolation. So I started r and accessed the help
> (help.start()). (by the way is it possible to configure r to open help
> in opera instead of firefox?) Initially I read the help for the akima
> package but couldn't understand it. Next I tried the asplines package
> help.
>
> I tried to copy the example: x<-c(-3,-2,...
>
> I realised that the 'n=...' parameter determines the resolution of the
> line, so I practised the following subsequent commands:
>
> > x<-c(-3,-2,-1,0,1,2,2.5,3)
> > y<-c(0,0,0,0,-1,-1,0,2)
> > plot(x,y,ylim=c(-3,3))
>
> I get the graph as expected
>
> Then I enter further commands:
>
> lines(spline(x,y,n=200),col="blue")
> lines(spline(x,y,n=20),col="blue")
> lines(spline(x,y,n=2),col="blue")
> lines(spline(x, y, n=5), col="blue")
>
> >From this I learn that n corresponds to line resolution. :)
>
> However I could not find a way to remove the last 3 commands and then
> show only the first line. How do I achieve this please?
>
> I am learning this package in order to perform my next task;
> interpolation.
>
> If I have a linear relationship between two variables and plot the
> results, how do I manipulate the graph to be able to show a value of
> the abscissa, especially for negative values, i.e. where the linear
> line intersects the x axis left of the y axis?
>
> There are 4 packages that claim interpolation (akima, aspline, interp,
> interpp) but they seem far to complicated, especially the latter two.
> Is there a simpler package I could use?
>
> Yours,
>
> rhelp at conference.jabber.org
>
> r 251 (27-06-07)
> mandriva 2008
>
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