##--------------------------------------------------------------------------------##
## ras: *RasterLayer object of binary raster with UTM projection and WGS84 datum
## opts: *SpatialPointsDataFrame object of observed locations
## radius: numeric object of length(opts) specifying location-specific 
##         maximum displacement buffer distance
##--------------------------------------------------------------------------------##
misclass <- function(ras, opts, radius){

	## extract cell value at observed point
	ptval <- extract(ras, opts, method="simple") 
	ptval[which(is.na(ptval))] <- 0 ## assign 0 to NA values
	
	## Calculate proportion of cells of type 1 within displacement buffer
	x <- extract(ras, opts, buffer=radius, na.rm=TRUE, fun=mean) 

	## Calculate misclassification probability for each observed location 
	mc <- numeric(length(ptval)) 
	mc[which(ptval==1)] <- 1-x[which(ptval==1)] 
	mc[which(ptval==0)] <- x[which(ptval==0)]
	list(pr.misclass=mc, misclass.rate=length(which(mc>0))/length(mc))
	}

##---------------------------------------------------------------------------------##
## Function returns a list of two objects:
## pr.misclass: numeric vector of length(opts) representing misclassification 
##				probabilities for each observed location
## misclass.rate: numeric value indicating the proportion of locations with 
##				  non-zero misclassification probabilities
##---------------------------------------------------------------------------------##