Supplementary material:

- mdrur-spiral.gif: GIF animation of a toy example of a 2D spiral
  with 30% missing data (y1 or y2). The missing values of Y were
  initialized at zeros. The top-left plot shows the mapping f (red line)
  and the contours of the mapping F. The top-right plot shows xn and
  F(yn). The Y--recY plot links the reconstructed recY vectors with the
  true Y. Note how recY follow the trace of f, and in turn this helps f
  improve. Although many vertical and horizontal lines remain in the
  Y--recY plot, the recY are not wrong (see the bottom-right plot); the
  lines indicate there are multiple plausible reconstructions, and the
  particular one selected differs from the true one.

All these animations may be seen with a web browser or with specialized
GIF image viewers.