[R-sig-Geo] How to apply a local polynomial regression function to a RasterStack object by "calc" function?

[Richard Ma]

Hi all, 

I have a RasterStack with 23 layers. Now I want to fit a local polynomial
regression through 23 layers. I use the package "KernSmooth" to fit the
regression function. 

Here is the example data, you can download them from my Dropbox folder, it's
a native raster package format: 
http://dl.dropbox.com/u/19228076/cmg_stack.grd
http://dl.dropbox.com/u/19228076/cmg_stack.gri

Here is my code: 
######################################### 
require(raster) 
require(KernSmooth) 

cmg.stack <- stack("cmg_stack.grd") 

# Calculate the bandwidth for each cell 
time <- seq(1, 353, 16)
gs <- 365
fun.bw <- function(x) dpill(x, x = time, gridsize = gs) 
bw <- calc(cmg.stack, fun.bw)  # This line works fine 

# Create a function to apply the "locpoly" function 
fun.lp <- function(x) {yvalues <- locpoly(x = time, y = x, bandwidth = bw,
gridsize = gs)$y 
return(yvalues)} 

#########################################
#### However, I got an error: 
#########################################

> cmg.stack.lp <- calc(cmg.stack, fun.lp, progress = "text") 
Error in .local(x, fun, ...) : cannot use this function 

######################################### 

Can you please point my problem? Is that possible to apply this function by
"calc"? Or are there any other solution to my question? 

Thanks in advance for any help. 

Sincerely, 
Richard


-----
Richard Ma
PhD student, Ecology & Remote Sensing
Climate Change Cluster, Department of Environment Science
University of Technology, Sydney
http://everydropr.wordpress.com
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