[ncl-talk] adjusting tension of a smooth overlaid on xyplot

[Mary Haley]

Hi Sam,

I'm not familiar with the "lowess" function in R.  Perhaps if you find this
useful, and we can get at the source code, we can add an interface to in
NCL?

I did try the same example using the lspoly function, but I think this
would be too smooth for your purposes.  See example interp1d_3.ncl at:

http://www.ncl.ucar.edu/Applications/interp1d.shtml#ex3

--Mary


On Fri, Aug 7, 2015 at 3:29 PM, Sam McClatchie (NOAA Federal) <
sam.mcclatchie at noaa.gov> wrote:

> Hello Mary -- Thanks for checking this out. I ran your script and the your
> plots have the same problem that my own script had. Namely, changing the
> tension parameter, sig, has almost no effect on the smooth. Perhaps it is
> the difference between what a physicist and a biologist might think of as
> smoothing ... I've attached a plot where I use your data to create smooths
> with different "tension". Since these smooths were created with locally
> weighted robust regression the tension is actually the span, or the
> proportion of the data used for each locally weighted fit. But the effect
> is what I am after. When you adjust the span, or tension, the curve becomes
> more or less smooth.
>
> Here is the R-code:
> # test.smooth.with.Haley.data
> library(RNetCDF, graphics)
> # load Marys test data and plot a subsample
> # ====================================
> nc <- open.nc("TestData.xy3.nc")
> dat <- read.nc(nc)
> print(summary(dat))
> yi <- dat$T[1:36]
>
> # fit a lowess smooth with differing spans
> # equivalent to tension on a smooth
> # ========================================
> pdf("test.smooth.pdf")
> plot(yi, type="b", ylab="Temperature")
> i <- seq(1,36,1)
> d <- cbind(i,yi)
> span <- seq(0.1,0.5,0.1)
> c <- seq(1,5,1)
> for(k in 1:length(span)) {
>     lines(lowess(d, f=span[k]), col=c[k])
> }
> graphics.off()
>
> Best fishes
> Sam
>
>
> On 08/07/2015 12:13 PM, Mary Haley wrote:
>
> Sam,
>
> Here's a slightly better example, that uses dummy data read off a NetCDF
> file. The script is pretty much the same, except I changed the data and
> added more tension factors to test. I also created a panel plot for
> comparison.
>
> I've also added this example to our 1D interpolators page:
>
> http://www.ncl.ucar.edu/Applications/interp1d.shtml#ex3
>
> --Mary
>
> On Fri, Aug 7, 2015 at 12:43 PM, Mary Haley <haley at ucar.edu> wrote:
>
>> Hi Sam,
>>
>> It appears you are using the parameter correctly.
>>
>> Please try running the attached example, which shows a simple XY plot,
>> and different tension factors using the "sig" parameter with ftcurv.
>>
>> If this doesn't shine a light on the problem at your end, then can you
>> provide us with a script and the data?
>>
>> --Mary
>>
>>
>> On Tue, Aug 4, 2015 at 5:07 PM, Sam McClatchie (NOAA Federal) <
>> <sam.mcclatchie at noaa.gov>sam.mcclatchie at noaa.gov> wrote:
>>
>>> Colleagues
>>>
>>> I want to put a smooth line through a de-seasonalized time series that
>>> shows a trend and residual variability. I'm having trouble adjusting the
>>> tension of the smooth which I think needs to be less than one. I would like
>>> the overlaid smooth curve to be much more smooth than the data, but I'm
>>> basically getting a high order polynomial smooth at present.
>>>
>>> Here is a snip of code:
>>>
>>> (Note: the xyplot tsplots(2) was previously defined)
>>>
>>> xi = (/spice_ts_ss&time/)
>>> yi = monthly_anom(:,0,0)
>>> xo = fspan(1985., 2015., 200)
>>> ftsetp("sig",0.5)
>>> yo = ftcurv(xi,yi,xo)
>>>
>>> colors = (/"red","green","blue"/)
>>> resplot at xyLineColor   = colors(0)
>>> tsplots(3)  = gsn_csm_xy (wks,xo,yo,resplot)
>>> overlay(tsplots(2), tsplots(3))
>>>
>>> Changing the value of the sig parameter in ftsetp between 0.1 to 40
>>> seems to have no effect, which suggests that I am misusing something?
>>>
>>> Thanks in advance,
>>> Sam
>>> --
>>> Sam McClatchie,
>>> Supervisory oceanographer,
>>> NOAA lead for the CalCOFI program
>>> Southwest Fisheries Science Center, NOAA,
>>> 8901 La Jolla Shores Dr.
>>> La Jolla, CA 92037-1509, U.S.A.
>>> email <Sam.McClatchie at noaa.gov> <Sam.McClatchie at noaa.gov>
>>> Office: 858 546 7083 <858%20546%207083>, Cellular:  858 752 8495
>>> <858%20752%208495>
>>> Research home page < <http://www.fishocean.info>www.fishocean.info>
>>> [image: CalCOFI 66 years]
>>>
>>> _______________________________________________
>>> ncl-talk mailing list
>>> ncl-talk at ucar.edu
>>> List instructions, subscriber options, unsubscribe:
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>>>
>>>
>>
>
> --
> Sam McClatchie,
> Supervisory oceanographer,
> NOAA lead for the CalCOFI program
> Southwest Fisheries Science Center, NOAA,
> 8901 La Jolla Shores Dr.
> La Jolla, CA 92037-1509, U.S.A.
> email <Sam.McClatchie at noaa.gov> <Sam.McClatchie at noaa.gov>
> Office: 858 546 7083, Cellular:  858 752 8495
> Research home page <www.fishocean.info>
> [image: CalCOFI 66 years]
>
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