Chapter 4: Plotting Axis Systems and Titles 4.1 Plotting Axis Systems An axis system defines an area on the page for plotting data. Various axis systems can be plotted to accommodate different applications. For two-dimensional graphics, a max- imum of two parallel X- and Y-axes can be drawn. The axis system is scaled to fit the range of data points and can be labeled with values, names and ticks. Two-dimensional axis systems are plotted with a call to the routine GRAF. G R A F GRAF plots a two-dimensional axis system. The call is: CALL GRAF (XA, XE, XOR, XSTEP, YA, YE, YOR, YSTEP) level 1 XA, XE are the lower and upper limits of the X-axis. XOR, XSTEP are the first X-axis label and the step be- tween labels. YA, YE are the lower and upper limits of the Y-axis. YOR, YSTEP are the first Y-axis label and the step be- tween labels. Notes: - GRAF must be called in level 1 and automati- cally sets the level to 2. When plotting more than 1 axis system on a page, ENDGRF must be called in between each new set of axes in or- der to set the level back to 1. - The position of the lower left corner and the size of an axis system can be changed with the routines AXSPOS and AXSLEN. - The axis scaling is linear by default and can be changed with SCALE. For logarithmic sca- ling, the corresponding parameters in GRAF must be exponents of base 10. - One of several label types can be chosen with the routine LABELS or user-defined with MYLAB. Single labels can be suppressed by calling AXENDS. - The routine NAME defines axis titles. - The number of ticks between axis labels can be changed with the routine TICKS. - SETGRF can be used to remove a piece of or complete axis from an axis system. - If the numerical value of the lower limit of an axis is larger than the upper limit and the label step is negative, axis scaling will be in descending order. - The routine FRAME defines the thickness of a frame plotted around an axis system. A frame can also be plotted outside of GRAF with the statement CALL BOX2D. 4.2 Termination of Axis Systems E N D G R F The routine ENDGRF terminates an axis system and sets the level back to 1. The call is: CALL ENDGRF level 2, 3 4.3 Plotting Titles T I T L E This routine plots a title over an axis system. The title may contain up to four lines of text designated with TITLIN. The call is: CALL TITLE level 2, 3 Note: All lines are centred by default but can be left- or right-justified using TITJUS. 4.4 Plotting Grid Lines G R I D The routine GRID overlays a grid on an axis system. The call is: CALL GRID (IXGRID, IYGRID) level 2, 3 IXGRID, IYGRID are the numbers of grid lines between la- bels. G R D P O L The routine GRDPOL plots a polar grid. The call is: CALL GRDPOL (IXGRID, IYGRID) level 2, 3 IXGRID is the numbers of circles between labels. IYGRID is the numbers of sector lines between 360 degrees. A X G I T The routine AXGIT plots vertical and horizontal lines through X = 0 and Y = 0. The call is: CALL AXGIT level 2, 3 Note: The statement CALL XAXGIT plots only the line Y = 0 while CALL YAXGIT plots only X = 0. C R O S S The routine CROSS plots vertical and horizontal lines with additional ticks through X = 0 and Y = 0. The call is: CALL CROSS level 2, 3 Note: The statement CALL XCROSS plots only the line Y = 0 while CALL YCROSS plots only X = 0. 4.5 Secondary Axes The following routines plot single X- and Y-axes; they are called secondary axes because they do not define or change any of the axis scaling parameters. Secondary axes can be used to add additional labels to the axis systems. The plotting routines for secondary axes are: XAXIS plots a linear X-axis. level 1, 2, 3 YAXIS plots a linear Y-axis. level 1, 2, 3 XAXLG plots a logarithmic X-axis. level 1, 2, 3 YAXLG plots a logarithmic Y-axis. level 1, 2, 3 The call is: CALL XAXIS (A, B, OR, STEP, NL, CSTR, IT, NX, NY) A, B are the lower and upper limits of the axis. OR, S are the first label and the step between la- bels. NL is the length of the axis in plot coordinates. CSTR is a character string containing the axis name. IT indicates how ticks, labels and the axis name are plotted. If IT = 0, they are plotted in a clockwise direction. If IT = 1, they are plot- ted in an counter-clockwise direction. NX, NY are the plot coordinates of the axis start point. The X-axis will be plotted from left to right and the Y-axis from bottom to top. Analog: YAXIS, XAXLG, YAXLG Notes: - Secondary axes can be called from level 1, 2 or 3. Note again that secondary axes do not change the scaling of an axis system defined by GRAF. Similarly, curves cannot be plotted with only secondary axes, they require a call to GRAF. - As in GRAF, the parameters of logarithmic axes must be exponents of base 10. - User-defined labels may also be plotted on secondary axes with MYLAB and the argument 'USER' in the routine LABELS. - The number of ticks can be changed by calling TICKS.