YLabelCenter Keyword
Used With Routines: AXIS,  BAR,  BAR2D,  BAR3D,  BOXPLOT,  CONTOUR,  CONTOURFS,  CONTOUR2,  OPLOT,   PLOT, PLOT_FIELD,  SURFACE
Corresponding System Variable: None.
Controls whether the top and bottom major tick labels on a Y axis will be positioned within the boundaries of the axis box or centered across from the corresponding major tick.
If this keyword is set, the top and bottom Y axis major tick labels will be centered vertically with corresponding major ticks. If this keyword is not set, the default behavior is to position the top and bottom Y axis major tick labels within the boundaries of the axis box.
Example
To produce a plot with with top and bottom major tick labels on the Y axis centered across from the corresponding major tick:
PLOT, DIST(20), YTICKS=10, /YLabelCenter