[gradsusr] Artifacts on charts

[Mike Manning]

Hi all,

I'm using this formula to hide any CAPE values below 500. It's working 
however there are black areas left on my map which when I overlay the 
contours over them it shows them as a value of 0 even though I have 
defined 0 with colour 17 (255,255,255). Has anyone else experienced this 
problem?

'define b=maskout(CAPE180_0mb,CAPE180_0mb-500)'
'define capeindex=const(const(b,1),0,-u)'

'set gxout shaded'
'set csmooth on'
'set clevs     0  500 1000 1800'
'set ccols  17 17  36   37   39'
'set cmin 0'

'd capeindex*CAPE180_0mb)'