R help - Jun 2012 - Do YOU know an equation for splines (ns)?

Hi, 

I am looking at the change in N concentration in plant roots over 4 time
points and I have fit a spline to the data using ns and lme: 

fit10 <- lme( N~ns(day, 3), data = rcn10G) 

I may want to adjust the model a little bit, but for now, let's assume
it's
good.  I get output for the fixed effects: 

Fixed: N ~ ns(day, 3) 
(Intercept) ns(day, 3)1 ns(day, 3)2 ns(day, 3)3 
 1.15676524  0.14509171  0.04459627  0.09334428 
  
and coefficients for each experimental unit in my experiment: 

   (Intercept) ns(day, 3)1 ns(day, 3)2 ns(day, 3)3 
24    1.050360 -0.42666159 -0.56290877 -0.10714407 
13    1.104464 -0.30825350 -0.53311653 -0.05558150 
31    1.147878 -0.14548512 -0.78673906 -0.07231781 
46    1.177781 -0.22278380 -0.80278177 -0.02321460 
15    1.144215 -0.04484519 -0.06084798  0.07633663 
32    1.213007  0.00741061  0.03896933  0.15325849 
23    1.274615  0.16477514  0.00872224  0.23128320 
41    1.215626  0.57050767  0.11415467  0.10608867 
43    1.134203  0.48070741  0.72112899  0.18108193 
12    1.091422  0.39563632  1.01521528  0.22597459 
21    1.100631  0.44589314  0.98526322  0.23535739 
35    1.226980  0.82419937  0.39809568  0.16900841 

NOW, I want to write a spline function where I can incorporate these
coefficients to get the predicted N concentration value for each day. 
However, I am having trouble finding the right spline equation, since there
are many forms on the internets.   

I know it won't be a simple one, but can some one direct me to the equation
that would be best to use for ns? 

Thanks a lot, 

Ranae 


--
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Does
?predict.ns
not do what you want without having to explicitly manipulate the spline basis?

-- Bert

On Tue, Jun 5, 2012 at 1:56 PM, Ranae <ranae.dietzel at gmail.com>
wrote:
> Hi,
>
> I am looking at the change in N concentration in plant roots over 4 time
> points and I have fit a spline to the data using ns and lme:
>
> fit10 <- lme( N~ns(day, 3), data = rcn10G)
>
> I may want to adjust the model a little bit, but for now, let's assume
it's
> good. ?I get output for the fixed effects:
>
> Fixed: N ~ ns(day, 3)
> (Intercept) ns(day, 3)1 ns(day, 3)2 ns(day, 3)3
> ?1.15676524 ?0.14509171 ?0.04459627 ?0.09334428
>
> and coefficients for each experimental unit in my experiment:
>
> ? (Intercept) ns(day, 3)1 ns(day, 3)2 ns(day, 3)3
> 24 ? ?1.050360 -0.42666159 -0.56290877 -0.10714407
> 13 ? ?1.104464 -0.30825350 -0.53311653 -0.05558150
> 31 ? ?1.147878 -0.14548512 -0.78673906 -0.07231781
> 46 ? ?1.177781 -0.22278380 -0.80278177 -0.02321460
> 15 ? ?1.144215 -0.04484519 -0.06084798 ?0.07633663
> 32 ? ?1.213007 ?0.00741061 ?0.03896933 ?0.15325849
> 23 ? ?1.274615 ?0.16477514 ?0.00872224 ?0.23128320
> 41 ? ?1.215626 ?0.57050767 ?0.11415467 ?0.10608867
> 43 ? ?1.134203 ?0.48070741 ?0.72112899 ?0.18108193
> 12 ? ?1.091422 ?0.39563632 ?1.01521528 ?0.22597459
> 21 ? ?1.100631 ?0.44589314 ?0.98526322 ?0.23535739
> 35 ? ?1.226980 ?0.82419937 ?0.39809568 ?0.16900841
>
> NOW, I want to write a spline function where I can incorporate these
> coefficients to get the predicted N concentration value for each day.
> However, I am having trouble finding the right spline equation, since there
> are many forms on the internets.
>
> I know it won't be a simple one, but can some one direct me to the
equation
> that would be best to use for ns?
>
> Thanks a lot,
>
> Ranae
>
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/Do-YOU-know-an-equation-for-splines-ns-tp4632440.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.


-- 

Bert Gunter
Genentech Nonclinical Biostatistics

Internal Contact Info:
Phone: 467-7374
Website:
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