findTuning: Find Tuning parameters for B-spline spatial deformation

In guiludwig/bsplinedef: Spatial Deformation via Tensor Product of B-splines

Description

This auxiliary function helps finding tuning parameters (lambda, zeta) for the B-spline tensor product spatial deformation. Execution might be slow.

Usage

findTuning(model, grid.lambda = 10^(-5:5),
  grid.zeta = min(apply(model$x, 2, function(x) diff(range(x)))) *
  (1:10)/20, verbose = FALSE)

Arguments

model	an object from the bdef function.
grid.lambda	Grid of values for the penalty parameter lambda.
grid.zeta	Grid of values for the penalty parameter zeta.
verbose	Verbose execution informs user of the LOOCV progress. Defaults to FALSE.

Value

a data frame with the selected grid, and the leave-one-out cross validation error

Examples

# Example using artificially generated data
## Not run: 
set.seed(1)
m <- 10
x1 <- (0:m)/m
x2 <- (0:m)/m
x <- as.matrix(expand.grid(x1,x2))
n <- nrow(x)
F1 <- function(x1,x2, a = 2.5, b = 1.0) {
x <- x1 - 0.5; y <- x2 - 0.5
angle <- a*exp(-(x*x+y*y)/(b*b)) + 3*pi/2
return(cos(angle)*x + sin(angle)*y + 0.5)
}
F2 <- function(x1,x2, a = 2.5, b = 1.0) {
x <- x1 - 0.5; y <- x2 - 0.5
angle <- a*exp(-(x*x+y*y)/(b*b)) + 3*pi/2
return(-sin(angle)*x + cos(angle)*y + 0.5)
}
TIME <- 20
covModel <- RMexp(var = 1, scale = .25, proj = "space") + RMnugget(var = 1) # Independent in time
data <- RFsimulate(covModel, x = F1(x[,1],x[,2]), y = F2(x[,1],x[,2]), 
                   T = seq(from = 1, by = 1, len = TIME)) # order ~ expand.grid(x, y, T)
y <- as.numeric(unlist(data@data))
# Model for spatial dependence, time is assumed independent
covModelM <- RMexp(var = NA, scale = NA) + RMnugget(var = NA)
# Calculates deformation, profle likelihood up to maxit times
test.def <- bdef(x, y, tim = 1:TIME, cov.model = covModelM, maxit = 10)
tuningChoice <- findTuning(test.def, verbose = TRUE)
require(ggplot2)
require(dplyr)
tuningChoice %>%
mutate(zeta = factor(zeta)) %>%
mutate(lambda = log(lambda)) %>%
ggplot(aes(x = lambda, y = LOOCV, color = zeta)) + 
geom_point() +
geom_line(aes(group = zeta))

## End(Not run)

guiludwig/bsplinedef documentation built on May 16, 2020, 10:24 p.m.