splot DATA using 1:2:3:4[:5] with zerrorfill {fc|fillcolor <colorspec>}
           {lt|linetype <n>} {<line properties>}

The zerrorfill plot style is similar to one variant of the 2D plot style filledcurves. It fills the area between two functions or data lines that are sampled at the same x and y points. It requires 4 or 5 input columns:

4 columns:  x  y  z  zdelta
5 columns:  x  y  z  zlow  zhigh

The area between zlow and zhigh is filled and then a line is drawn through the z values. By default both the line and the fill area use the same color, but you can change this in the splot command. The fill area properties are also affected by the global fill style; see set style fill.

If there are multiple curves in the splot command each new curve may occlude all previous curves. To get proper depth sorting so that curves can only be occluded by curves closer to the viewer, use set pm3d depthorder base. Unfortunately this causes all the filled areas to be drawn after all of the corresponding lines of z values. In order to see both the lines and the depth-sorted fill areas you probably will need to make the fill areas partially transparent or use pattern fill rather than solid fill.

The fill area in the first two examples below is the same.

splot 'data' using 1:2:3:4 with zerrorfill fillcolor "grey" lt black
splot 'data' using 1:2:3:($3-$4):($3+$4) with zerrorfill
splot '+' using 1:(const):(func1($1)):(func2($1)) with zerrorfill
splot for [k=1:5] datafile[k] with zerrorfill lt black fc lt (k+1)

This plot style can also be used to create fence plots. See fenceplots.

Copyright 1986 - 1993, 1998, 2004 Thomas Williams, Colin Kelley
Distributed under the gnuplot license (rights to distribute modified versions are withheld).