[R] loess plotting problem

[Anupam Tyagi]

Thanks, John.

However, loess.smooth() is producing a very different curve compared to the
one that results from applying predict() on a loess(). I am guessing they
are using different defaults. Correct?


On Thu, 23 Mar 2023 at 20:20, John Fox <jfox using mcmaster.ca> wrote:

> Dear Anupam Tyagi,
>
> You didn't include your data, so it's not possible to see exactly what
> happened, but I think that you misunderstand the object that loess()
> returns. It returns a "loess" object with several components, including
> the original data in x and y. So if pass the object to lines(), you'll
> simply connect the points, and if x isn't sorted, the points won't be in
> order. Try, e.g.,
>
> plot(speed ~ dist, data=cars)
> m <- loess(speed ~ dist, data=cars)
> names(m)
> lines(m)
>
> You'd do better to use loess.smooth(), which is intended for adding a
> loess regression to a scatterplot; for example,
>
> plot(speed ~ dist, data=cars)
> with(cars, lines(loess.smooth(dist, speed)))
>
> Other points: You don't have to load the stats package which is
> available by default when you start R. It's best to avoid attach(), the
> use of which can cause confusion.
>
> I hope this helps,
>   John
>
> --
> * preferred email: john.david.fox using proton.me
> John Fox, Professor Emeritus
> McMaster University
> Hamilton, Ontario, Canada
> web: https://www.john-fox.ca/
>
> On 2023-03-23 10:18 a.m., Anupam Tyagi wrote:
> > For some reason the following code is not plotting as I want it to. I
> want
> > to plot a "loess" line plotted over a scatter plot. I get a jumble, with
> > lines connecting all the points. I had a similar problem with "lowess". I
> > solved that by dropping "NA" rows from the data columns. Please help.
> >
> > library(stats)
> > attach(gini_pci_wdi_narm)
> > plot(ny_gnp_pcap_pp_kd, si_pov_gini)
> > lines(loess(si_pov_gini ~ ny_gnp_pcap_pp_kd, gini_pci_wdi_narm))
> > detach(gini_pci_wdi_narm)
> >
>
>

-- 
Anupam.

	[[alternative HTML version deleted]]