[R] Tps error

[Jennifer Gremer]

Hi,
I am trying to use the Tps procedure to visualize 3 variables in XYZ space, but
keep getting the error messages below:
Warning messages:
1: In Krig.find.gcvmin(info, lambda.grid, gcv.grid$GCV, Krig.fgcv,  :
  GCV search gives a minimum at the endpoints of the
grid search
2: In Krig.find.gcvmin(info, lambda.grid, gcv.grid$GCV.one, Krig.fgcv.one,  :
  GCV search gives a minimum at the endpoints of the
grid search

This is the code I am using:
tpsfit <- Tps(cbind(x1, x2), Y, scale.type = "unscaled")

I have successfully used the Tps function for other subsets of the data, but one
set is problematic.  The output suggests that the smoothing parameter (lambda)
is very low (5.632e-05).  I have also attached the rest of the output from the
function below this email.

Can anyone help me with this problem?  I can send an example of the data I am
using if that is helpful.

Any feedback would be appreciated.
Thank you,
Jenny

CALL:
Tps(x = cbind(x1, x2), Y = Y, scale.type = "unscaled", cov.function = "Thin
plate spline radial basis functions (Rad.cov) ")

 Number of Observations:                116
 Number of unique points:               116
 Number of parameters in the null space 3
 Parameters for fixed spatial drift     3
 Effective degrees of freedom:          110.2
 Residual degrees of freedom:           5.8
 MLE sigma                              0.03841
 GCV sigma                              0.05004
 MLE rho                                26.2
 Scale passed for covariance (rho)      <NA>
 Scale passed for nugget (sigma^2)      <NA>
 Smoothing parameter lambda             5.632e-05

Residual Summary:
       min      1st Q     median      3rd Q        max
-0.0339500 -0.0054520  0.0002131  0.0044340  0.0351400

Covariance Model: Rad.cov
  Names of non-default covariance arguments:
       p

DETAILS ON SMOOTHING PARAMETER:
 Method used:   GCV    Cost:  1
   lambda       trA       GCV   GCV.one GCV.model      shat
5.632e-05 1.102e+02 5.007e-02 5.007e-02        NA 5.004e-02

 Summary of all estimates found for lambda
              lambda     trA     GCV    shat   REML
GCV        5.632e-05 110.200 0.05007 0.05004 40.029
GCV.model         NA      NA      NA      NA     NA
GCV.one    5.632e-05 110.200 0.05007 0.05004     NA
RMSE              NA      NA      NA      NA     NA
pure error        NA      NA      NA      NA     NA
REML       8.520e+03   3.001 0.06374 0.24919  3.323



Jennifer R. Gremer
Postdoctoral Research Associate
Ecology and Evolutionary Biology
University of Arizona
mail: P.O. 210088
deliveries: Biosciences West, Room 310
Tucson, AZ 85721
office: 520-621-4022