suppress the grid and labels altogether. The default for this option is
to automatically select sensible values.
+If you have set --y-grid to 'none' not only the labels get supressed, also
+the space reserved for the labels is removed. You can still add space
+manually if you use the --units-length command to explicitly reserve space.
+
[B<-Y>|B<--alt-y-grid>]
Place the Y grid dynamically based on the graph's Y range. The algorithm