Re: FW: lspoly didn't wok when the number of data points equal to the number of coefficients

Hi, Dennis
I could not wait the next version of NCL since my project is urgent. Can I use the lspoly_ncl.f you sent to me in NCL$B!)(B How to use it ? Do you have the slatec_lspoly function in NCL
Thanks


> Date: Wed, 1 Jan 2014 09:13:04 -0700
> From: shea@ucar.edu
> To: richardljy@hotmail.co.uk; ncl-talk@ucar.edu
> Subject: Re: [ncl-talk] FW: lspoly didn't wok when the number of data points equal to the number of coefficients
>
> The lspoly used thru NCL v6.1.2 has some known limitations.
> The next release (v6.2.0) will hopefully contain an updated version of
> lspoly. Here called 'slatec_lspoly'. The following test script
> and the results illustrates the issues.
>
> A comparison to R results follows.
>
> ==> NCL script
>
> x = (/-4.5, -3.2, -1.4/)
> y = (/ 0.7, 2.3, 3.8/)
>
> n = dimsizes(y)
>
> print(" ")
> print("===========> 6.1.2 <===========")
> print(" ")
>
> n1 = n-1 ; max # of coef returned by lspoly
> ; n1=2
> c = lspoly(x,y, 1, n1) ; up thru 6.1.2
> cc = slatec_lspoly(x,y, 1, n1) ; 6.2.0
>
> print(c)
> print(cc)
>
> cx = lspoly(x,y, 1, n) ; n=3 will fail
> print(cx)
>
> print(" ")
> print("===========> 6.2.0 <===========")
> print(" ")
>
> cc3 = slatec_lspoly(x,y, 1, n) ; n=3 here
> print(cc3)
>
> *************************************************
>
> (0)
> (0) ===========> 6.1.2 <===========
> (0)
>
> Variable: c
> Type: float
> Total Size: 8 bytes
> 2 values
> Number of Dimensions: 1
> Dimensions and sizes: [2]
> Coordinates:
> (0) 5.268707
> (1) 0.9896836
>
> Variable: cc
> Type: float
> Total Size: 8 bytes
> 2 values
> Number of Dimensions: 1
> Dimensions and sizes: [2]
> Coordinates:
> (0) 5.268707
> (1) 0.9896836
>
> Variable: cx <=== fail
> Type: float
> Total Size: 12 bytes
> 3 values
> Number of Dimensions: 1
> Dimensions and sizes: [3]
> Coordinates:
> (0) 1e+20
> (1) 1e+20
> (2) 1e+20
>
> (0)
> (0) ===========> 6.2.0 <===========
> (0)
>
> Variable: cc3 match R results
> Type: float
> Total Size: 12 bytes
> 3 values
> Number of Dimensions: 1
> Dimensions and sizes: [3]
> Coordinates:
> (0) 4.392307
> (1) 0.2435896
> (2) -0.1282052
>
>
>
> ***********************************************
> ------ Using R --------------------------------
> ************************************************
>
> > x <- c(-4.5, -3.2, -1.4)
> > y <- c(0.7, 2.3, 3.8)
> > n <- 1 # degree of polynomial
> > result <- lm( y ~ poly( x, n, raw=T))
>
> > result
>
> Call:
> lm(formula = y ~ poly(x, n, raw = T))
>
> Coefficients:
> (Intercept) poly(x, n, raw = T)
> 5.2687 0.9897
>
> ---------------------
>
> > n <- 2 # degree of polynomial
> > result <- lm( y ~ poly(x,n, raw=T))
> > result
>
> Call:
> lm(formula = y ~ poly(x, n, raw = T))
>
> Coefficients:
> (Intercept) poly(x, n, raw = T)1 poly(x, n, raw = T)2
> 4.3923 0.2436 -0.1282
>
> On 12/31/13, 8:18 PM, Richard Liang wrote:
> > Thanks. Dennis. But the problem remain: Mathematically, if I have 3 points, I can make an second order polynomial to fit these points , in which I should have 3 coefficients.
> > Thanks
> >
> >> Date: Mon, 30 Dec 2013 09:35:37 -0700
> >> From: shea@ucar.edu
> >> To: richardljy@hotmail.co.uk; ncl-talk@ucar.edu
> >> Subject: Re: [ncl-talk] FW: lspoly didn't wok when the number of data points equal to the number of coefficients
> >>
> >> The Description section documentation was not correct. It has been changed.
> >>
> >> On 12/29/13, 9:53 AM, Richard Liang wrote:
> >>> Thanks, Dennis
> >>> The document said "It is necessary that the number of data points) be greater than or equal to n(the number of coefficients)."
> >>> As I understand , for example, if I have 3 points, the max number of coefficients can be 3.
> >>> Mathematically, if I have 3 points, I can make an secend order polynomial to fit these points , in which I should have 3 coefficients.
> >>>
> >>> Best
> >>>
> >>>> Date: Sat, 28 Dec 2013 08:26:49 -0700
> >>>> From: shea@ucar.edu
> >>>> To: richardljy@hotmail.co.uk; ncl-talk@ucar.edu
> >>>> Subject: Re: [ncl-talk] FW: lspoly didn't wok when the number of data points equal to the number of coefficients
> >>>>
> >>>> As noted in the documentation:
> >>>>
> >>>> n
> >>>>
> >>>> The number of coefficients desired (i.e., n-1 will be the degree of the
> >>>> polynomial). Due to the method used, n should be less than or equal to
> >>>> five.
> >>>>
> >>>> ===
> >>>>
> >>>> In your case with 3 points, the max number of coefficients would be 2
> >>>>
> >>>>
> >>>> On 12/28/13, 5:01 AM, Richard Liang wrote:
> >>>>>
> >>>>>
> >>>>> From: richardljy@hotmail.co.uk
> >>>>> To: ncl-talk@ucar.edu
> >>>>> Subject: lspoly didn't wok when the number of data points equal to the number of coefficients
> >>>>> Date: Sat, 21 Dec 2013 15:45:08 -0500
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> lspoly didn't wok when the number of data points equal to the number of coefficientsI did the test
> >>>>> x = (/-4.5, -3.2, -1.4/)y = (/ 0.7, 2.3, 3.8/)n = 3 c = lspoly(x,y, 1, n) print(c)c will be(0) 1e+20(1) 1e+20(2) 1e+20
> >>>>>
> >>>>>
> >>>>> But if n=2 c will be(0) 5.268707(1) 0.9896836
> >>>>> I also did the test in the 4 element array, when n=4, it didn't work. only when n is less than the number of data points
> >>>>> Any body help me? thanks
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> _______________________________________________
> >>>>> ncl-talk mailing list
> >>>>> List instructions, subscriber options, unsubscribe:
> >>>>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
> >>>>>
> >>>
> >>>
> >
> >
                                               

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Received on Thu Jan 02 07:17:23 2014