Connect the data points or not?

 




This graph shows 6 terrain parameters, which are only very indirectly related, plotted against the FUV (fraction of unexplained variance, 1-r squared).  It shows one test DEM (satellite radar derived) versus a reference DTM (lidar derived).  Low value is best, so ELEV (elevation) agrees very closely, whereas TPI does not.

Because they are not related, some of my colleagues prefer the version on the bottom. I prefer the one on top because:

  • With the lines, it is clear that the urban category is the best (largest FUV).  With the points, it is much less obvious.
  • Despite the attempt to use both colors and different symbols, it is very hard to see all the values when they are close (say with RUFF, roughness).  With the lines, that is clear.
  • Where lines cross, the relative rankings change and it's clear (say shrubs, between HILL, hillshade, and SLOPE).
  • It might not be clear that all the categories are in fact present for the ELEV.
As long at the graph is explained, I think connecting with lines improves the graphic.

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