# Chapter 8: Elementary Plot Routines

This chapter describes elementary subroutines that plot lines, vectors, circles, ellipses, pie segments and polygons. There are versions for plot and user coordinates; the routines for user coordinates begin with the keyword 'RL'. These routines can only be called from level 2 or 3 after an axis system has been defined.

## 8.1 Lines

XMOVE and XDRAW are simple subroutines for plotting lines. They require absolute page coordinates and are, therefore, not affected by a call to ORIGIN. Different line styles cannot be used. The routine XMOVE moves the pen to a point while XDRAW draws a line to a point.

 The calls are: CALL XMOVE (X, Y) level 1, 2, 3 CALL XDRAW (X, Y) level 1, 2, 3

 or: void xmove (float x, float y); void xdraw (float x, float y);

 X, Y are absolute page coordinates.

The subroutines STRTPT and CONNPT require plot coordinates as real numbers and allow different line styles to be used.

 The calls are: CALL STRTPT (X, Y) level 1, 2, 3 CALL CONNPT (X, Y) level 1, 2, 3

 or: void strtpt (float x, float y); void connpt (float x, float y);

 X, Y are real numbers containing the plot coordinates.

The corresponding routines for user coordinates are:

 The calls are: CALL RLSTRT (X, Y) level 2, 3 CALL RLCONN (X, Y) level 2, 3

 or: void rlstrt (float x, float y); void rlconn (float x, float y);

 Additional note: Lines plotted with RLSTRT and RLCONN will not be cut off at the borders of an axis system. This can be enabled with the routine CLPBOR. Points lying outside of the axis scaling will not be listed by RLSTRT and RLCONN.

LINE joins two points with a line. Different line styles can be used.

 The call is: CALL LINE (NX, NY, NU, NV) level 1, 2, 3 or: void line (int nx, int ny, int nu, int nv);

 NX, NY are the plot coordinates of the first point. NU, NV are the plot coordinates of the second point.

RLINE is the corresponding routine for user coordinates.

 The call is: CALL RLINE (X, Y, U, V) level 2, 3 or: void rline (float x, float y, float u, float v);

 X, Y are the user coordinates of the first point. U, V are the user coordinates of the second point.

• RLINE draws only that part of the line lying inside the axis system. If NOCHEK is not used, points lying outside the axis scaling will be listed.

## 8.2 Vectors

V E C T O R

VECTOR plots vectors with none, one or two arrow heads.

 The call is: CALL VECTOR (IX1, IY1, IX2, IY2, IVEC) level 1, 2, 3 or: void vector (int ix1, int iy1, int ix2, int iy2, int ivec);

 IX1, IY1 are the plot coordinates of the start point. IX2, IY2 are the plot coordinates of the end point. IVEC is an integer number that defines the form of the arrow heads. If IVEC = -1, the arrow head can be defined with the routine VECOPT. Otherwise, IVEC can contain a four digit number 'wxyz' specifying the arrow heads where the digits have the following meaning: (see appendix B for examples)

```      w:      determines  the  ratio  of  width  and  length
(0 - 9).
x:      determines the size (0 - 9).
y:      determines the form:
= 0  filled
= 1  not filled
= 2  opened
= 3  closed
= 4  sharp, filled
= 5  sharp, not filled.
z:      determines the position:
= 0  no arrow heads are plotted
= 1  at end points
= 2  at start and end points
= 3  at start and end points and in the same direction.
```
R L V E C

RLVEC is the corresponding routine for user coordinates.

 The call is: CALL RLVEC (X1, Y1, X2, Y2, IVEC) level 2, 3 or: void rlvec (float x1, float y1, float x2, float y2, int ivec);

VECCLR defines the colour of arrow heads, or enables colour scaling in the routines FIELD, VECFLD, FIELD3D and VECF3D.

 The call is: CALL VECCLR (NCLR) level 1, 2, 3 or: void vecclr (int nclr);

 NCLR is a colour number. If ICLR has the value -2, colour scaling is enabled in vector fields. If ICLR = -1, arrow heads are plotted in the foreground colour. Otherwise, arrow heads are plotted in the colour ICLR. Default: ICLR = -1.

VECOPT defines some vector options such as the size of arrow heads and the appearance of user-defined arrows that are enabled with the vector number -1 in VECTOR and RLVEC. The routine can also disable automatic scaling of vectors in vector fields.

 The call is: CALL VECOPT (XOPT, CKEY) level 1, 2, 3 or: void vecopt (float xopt, const char *ckey);

 XOPT contains a floating point option. CKEY is a character string that can have one of the following values: = ANGLE defines the angle in degrees that is used for arrow heads plotted with the vector number -1. = LENGTH defines the ratio of the arrow head and vector length for vectors plotted with the number -1. = SCALE sets a scaling factor that is used for the vector length in vector field routines such as VECFLD and VECMAT. If XOPT = 0., automatic scaling is enabled. = SIZE defines a scaling factor for the size of arrow heads. Defaults: (20., 'ANGLE'), (0.25, 'LENGTH'), (0., 'SCALE'), (1.0, 'SIZE').

## 8.3 Filled Triangles

T R I F L L

The routine TRIFLL plots solid filled triangles.

 The call is: CALL TRIFLL (XRAY, YRAY) level 1, 2, 3 or: void trifll (const float *xray, const float *yray);

 XRAY, YRAY are floating point arrays containing the three corners of a triangle.

The routine TRIFLC plots solid filled triangles with interpolated colours.

 The call is: CALL TRIFLC (XRAY, YRAY, ICRAY, N) level 1, 2, 3 or: void triflc (const float *xray, const float *yray, const int *icray, int n);

 XRAY, YRAY are floating point arrays containing triangle corners. ICRAY are the colour values of the triangle corners. N is the number of points in the arrays above. N should be a multiple of three. You can increase performance by passing multiple triangles to TRIFLC instead of calling TRIFLC several times.

## 8.4 Wind Speed Symbols

W I N D B R

The routine WINDBR plots wind speed symbols (wind barbs).

 The call is: CALL WINDBR (X, NXP, NYP, NW, A) level 1, 2, 3 or: void windbr (float x, int nxp, int nyp, int nw, float a);

 X is the wind speed in knots. NXP, NYP are the plot coordinates of the lower left corner of the wind speed symbol. NW is the length of the symbol in plot coordinates. If NW < 0, the wind flags are plotted on the opposite site as usual in the southern hemisphere. A is the wind direction in degrees.

RLWIND is the corresponding routine to WINDBR for user coordinates.

 The call is: CALL RLWIND (X, XP, YP, NW, A) level 2, 3 or: void rlwind (float x, float xp, float yp, int nw, float a);

## 8.5 Geometric Figures

The following subroutines plot geometric figures such as rectangles, circles, ellipses, pie segments and polygons. These routines can be used to plot only the outlines of figures or the figures can be filled in with shaded patterns.

RECTAN plots rectangles.

 The call is: CALL RECTAN (NX, NY, NW, NH) level 1, 2, 3 or: void rectan (int nx, int ny, int nw, int nh);

 NX, NY are the plot coordinates of the upper left corner. NW, NH are the width and height in plot coordinates.

RECTAN plots an rectangle where the corners will be rounded.

 The call is: CALL RNDREC (NX, NY, NW, NH, IOPT) level 1, 2, 3 or: void rndrec (int nx, int ny, int nw, int nh, int iopt);

 NX, NY are the plot coordinates of the upper left corner. NW, NH are the width and height in plot coordinates. IOPT defines the rounding of corners (0 <= IOPT <= 9). For IOPT = 0, rounding is disabled.

CIRCLE plots circles.

 The call is: CALL CIRCLE (NX, NY, NR) level 1, 2, 3 or: void circle (int nx, int ny, int nr);

 NX, NY are the plot coordinates of the centre point. NR is the radius in plot coordinates.

ELLIPS plots ellipses.

 The call is: CALL ELLIPS (NX, NY, NA, NB) level 1, 2, 3 or: void ellips (int nx, int ny, int na, int nb);

 NX, NY are the plot coordinates of the centre point. NA, NB are the radii in plot coordinates.

PIE plots pie segments.

 The call is: CALL PIE (NX, NY, NR, ALPHA, BETA) level 1, 2, 3 or: void pie (int nx, int ny, int nr, float alpha, float beta);

 NX, NY are the plot coordinates of the centre point. NR is the radius in plot coordinates. ALPHA, BETA are the start and end angles measured in degrees in a counter-clockwise direction.

ARCELL plots elliptical arcs where the arcs can be rotated.

 The call is: CALL ARCELL (NX, NY, NA, NB, ALPHA, BETA, THETA) level 1, 2, 3 or: void arcell (int nx, int ny, int na, int nb, float alpha, float beta, float theta);

 NX, NY are the plot coordinates of the centre point. NA, NB are the radii in plot coordinates. ALPHA, BETA are the start and end angles measured in degrees in a counter-clockwise direction. THETA is the rotation angle measured in degrees in a counter-clockwise direction.

AREAF draws polygons.

 The call is: CALL AREAF (NXRAY, NYRAY, N) level 1, 2, 3 or: void areaf (const int *nxray, const int *nyray, int n);

 NXRAY, NYRAY are arrays containing the plot coordinates of the corner points. Start and end points can be different. N is the number of points.

 The calls are: CALL RLREC (X, Y, WIDTH, HEIGHT) level 2, 3 CALL RLRND (X, Y, WIDTH, HEIGHT, IOPT) level 2, 3 CALL RLCIRC (XM, YM, R) level 2, 3 CALL RLELL (XM, YM, A, B) level 2, 3 CALL RLPIE (XM, YM, R, ALPHA, BETA) level 2, 3 CALL RLARC (XM, YM, A, B, ALPHA, BETA, THETA) level 2, 3 CALL RLAREA (XRAY, YRAY, N) level 2, 3

 or: void rlrec (float x, float y, float width, float height) void rlrnd (float x, float y, float width, float height, int iopt) void rlcirc (float xm, float ym, float r) void rlell (float xm, float ym, float a, float b) void rlpie (float xm, float ym, float r, float alpha, float beta) void rlarc (float xm, float ym, float a, float b, float alpha, float beta, float theta) void rlarea (const float *xray, const float *yray, int n)

• Shading patterns can be defined with SHDPAT and MYPAT. If the pattern number is zero, the figures will only be outlined. With CALL NOARLN, the outline will be suppressed.
• The number of points in AREAF and RLAREA is limited to 25000 for Fortran 77 programs. There is no limitation for Fortran 90 and C programs.
• For the calculation of the radius in RLCIRC and RLPIE, the X-axis scaling is used.
• The interpolation of circles and ellipses can be altered with CIRCSP (NSPC) where NSPC is the arc length in plot coordinates. The default value is 10.

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