7.2.3 Coordinate Axis Routines

The usdaxs sets appropriate intervals for tick marks and labels for the currently set transformation function and creates a plot. The position of the coordinate axis is specified by the internal variable cxside/cyside of uscset, and the titles, etc. can be set using  ussttl or uscset. usdaxs basically processes the X ands Y axes independently, and it performs a different processing for determining the label interval depending on the angle between the label and the axis (parallel or perpendicular). Normally, the labels are drawn horizontally for both the X and Y axes (parallel to the X axis), so even when the data range for the X and Y axes are the same, the label interval may be different. If you are not comfortable with this, set 'LMATCH' to .true. with  uslset. Then, regardless of the direction of the label, the label interval is set assuming that the label is drawn parallel to the axis, so the intervals for X- and Y- axis labels will be the same.

The usdaxs  plot both the X and Y axes, but there is also the usxaxs and usyaxs for plotting the axes separately.