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variable: $colscalebarflag -- scalebar switch
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default: 0 (off)

The scalebar is linear plot of statistic color
that extends from {-maxval,maxval} where:

      maxval = fmid + (1.0/fslope)

For example, for fmid=0.5 and fslope=5.0,
scalebar is -0.7 to 0.7.
