R/Minb.R

In hadjipantelis/tPACE: Functional Data Analysis and Empirical Dynamics

# This function is used to find the minimum bandwidth choice
# where the local window contains at least "numPoints" points
# Input x  : n x 1 vector
# Input numPoints: an integer specifying the number of points in a local window
# for local weighted constant, numPoints is at least 1
# for local weighted linear, numPoints is at least 2
# Output b: the minimum bandwidth choice for vector x

Minb <- function(x, numPoints){ 
  
    n = length(x);
    if( (numPoints<1) || (numPoints > n) ){
      warning("Invalid number of minimum points specified\n")
      return(NaN)
    }
  
  if('legacyCode' == TRUE){
    x = sort(unique(x));     # Unique is added to ensure that we do not have a degenerate design
    if(numPoints > 1){ 
      return( max(x[numPoints:n]-x[1:(n-numPoints+1)]) )
    }else{ 
      return( max(   (x[2:n]-x[1:(n-1)])/2)   )
    } 
  }
  
  gridPts <- sort(unique(x))
  distNN1 <- max(diff(gridPts, lag=numPoints))
  
  return(distNN1)
}