R/assess_median_na_proportion.R

In heike/DS401: Quality Assessment of Scans of Land Engraved Areas on Fired Bullets

#' Feature Extraction: Median of the proportion of NA values present in the middle of a 3d scan,
#' from a specific number of different y values.
#'
#' One of the main problems with 3d scans are the feathering that occurs within the middle of the scan.
#' Here, we quantify this feathering by taking samples at specific number of y values in the surface matrix
#' that are in a certain percentage of the middle of the 3d scan. Then with these rows of the surface matrix we measure
#' the proportion of missing values in each of those rows. We then take the median proportion of missing values
#' of those rows, which will give us a good measure to quantify the amount of feathering in a 3d scan.
#' @param x3p scan in x3p format
#' @param chopoff numeric value between 0 and .5 - The percentage of values to chop off of both sides of the scan
#' @param numlines Number of horizontal lines across the scan to find the median proportion of na values from
#' @return median proportion of missing values
#' @importFrom stats median
#' @export
#' @examples
#' data(fau277_bb_l2)
#' assess_median_na_proportion(fau277_bb_l2)
assess_median_na_proportion <- function(x3p, chopoff = 1/6, numlines = 20) {
  # median is 50th percentile :) wrapper will give the same results
  assess_percentile_na_proportion(x3p = x3p, chopoff = chopoff, numlines = numlines, percentile = .50)

  # stopifnot(class(x3p) == "x3p")
  #
  # SurfaceMatrix <- x3p$surface.matrix
  #
  # NumberOfLines <- numlines - 2
  #
  # NumberofYIncrements <- x3p$header.info$sizeY
  #
  # NumberOfIncrementsBetweenLines <- floor(NumberofYIncrements/NumberOfLines)
  #
  # MaximumX <- x3p$header.info$sizeX*x3p$header.info$incrementX
  #
  # LowerXBound <- MaximumX * chopoff
  #
  # UpperXBound <- MaximumX - (MaximumX * chopoff)
  #
  # LowerYBound <- 0
  #
  # UpperYBound <- x3p$header.info$sizeY*x3p$header.info$incrementY
  #
  # IndexLowerXBound <- floor(LowerXBound/x3p$header.info$incrementX)
  #
  # IndexUpperXBound <- ceiling(UpperXBound/x3p$header.info$incrementX)
  #
  # SurfaceMatrix <- SurfaceMatrix[IndexLowerXBound:IndexUpperXBound,]
  #
  # ProportionNA <- vector(mode = "numeric",length = NumberOfLines+1)
  #
  # ProportionNA[1] <- mean(is.na(SurfaceMatrix[,1]))
  #
  # for(i in 1:(NumberOfLines-1)){
  #   ProportionNA[i+1] <- mean(is.na(SurfaceMatrix[,i*NumberOfIncrementsBetweenLines]))
  # }
  #
  # ProportionNA[NumberOfLines + 1] <- mean(is.na(SurfaceMatrix[,x3p$header.info$sizeY]))
  #
  # Median <- median(ProportionNA)
  #
  # return(Median)
}