dist.images {curveDepth}

Distance for images

Description

Calculates distance matrix for a sample of images using the minimax metric. This fucntion can be seen as a wrapper of a sequential call of images2curves and dist.curves.

Usage

dist.images(images, verbosity = 0L)

Arguments

images

A 3-dimensional array with each slice (matrix in first two dimensions) corresponding to an image. Each (eps-strictly) positive entry is regarded as an occupied pixel (one), otherwise it is regarded as an empty pixel, of an image.

verbosity

Level of reporting messages, the higher the more progress reports are printed, set 0 (default) for no messages.

Value

A matrix dim(images)[3] x dim(images)[3] with each entry being the distance between two images.

References

Lafaye De Micheaux, P., Mozharovskyi, P. and Vimond, M. (2018). Depth for curve data and applications.

Examples

library(curveDepth)
# Pixel-grid filling function for an image
plotGridImage <- function(dims){
  redDims1 <- dims[1] - 1
  redDims2 <- dims[2] - 1
  for (i in 1:(dims[1] - 1)){
    lines(c(i / redDims1 - 0.5 / redDims1,
            i / redDims1 - 0.5 / redDims1),
          c(0 - 0.5 / redDims2, 1 + 0.5 / redDims2),
          lwd = 1, lty = 3, col = "lightgray")
    lines(c(0 - 0.5 / redDims1, 1 + 0.5 / redDims1),
          c(i / redDims2 - 0.5 / redDims2,
            i / redDims2 - 0.5 / redDims2),
          lwd = 1, lty = 3, col = "lightgray")
  }
  rect(0 - 0.5 / redDims1, 0 - 0.5 / redDims2,
       1 + 0.5 / redDims1, 1 + 0.5 / redDims2)
}
# Load two Sevens and one One, and plot them
data("mnistShort017")
# First Seven
  firstSevenDigit <- mnistShort017$`7`[, , 5]
image(as.matrix(rev(as.data.frame(firstSevenDigit))),
      col = gray((255:0) / 256), asp = 1,
      xlim = c(0 - 1 / 27, 1 + 1 / 27),
      ylim = c(0 - 1 / 27, 1 + 1 / 27))
plotGridImage(dim(firstSevenDigit)[1:2])
# Second Seven
secondSevenDigit <- mnistShort017$`7`[, , 6]
image(as.matrix(rev(as.data.frame(secondSevenDigit))),
      col = gray((255:0) / 256), asp = 1,
      xlim = c(0 - 1 / 27, 1 + 1 / 27),
      ylim = c(0 - 1 / 27, 1 + 1 / 27))
plotGridImage(dim(secondSevenDigit)[1:2])
# A One
aOneDigit <- mnistShort017$`1`[, , 1]
image(as.matrix(rev(as.data.frame(aOneDigit))),
      col = gray((255:0) / 256), asp = 1,
      xlim = c(0 - 1 / 27, 1 + 1 / 27),
      ylim = c(0 - 1 / 27, 1 + 1 / 27))
plotGridImage(dim(aOneDigit)[1:2])
# Caculate distances between all the images
threeDigits <- array(NA, dim = c(nrow(firstSevenDigit),
  ncol(firstSevenDigit), 3))
threeDigits[, , 1] <- firstSevenDigit
threeDigits[, , 2] <- secondSevenDigit
threeDigits[, , 3] <- aOneDigit
distMatrix <- dist.images(threeDigits)
# Print distance matrix
print(distMatrix)