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Dataplot Vol 2 Vol 1

SLOPE

Name:
    SLOPE (LET)
Type:
    Library Function
Purpose:
    Return the slope between two points.
Description:
    Given two points, (X1,Y1) and (X2,Y2), the slope is defined as

      m = (Y2-Y1)/(X2-X1)
Syntax:
    LET <y> = SLOPE(<x1>,<y1>,<x2>,<y2>)
                            <SUBSET/EXCEPT/FOR qualification>
    where <x1> is a variable or a parameter containing the x coordinates of the first point;
                <y1> is a variable or a parameter containing the y coordinates of the first point;
                <x2> is a variable or a parameter containing the x coordinates of the second point;
                <y2> is a variable or a parameter containing the y coordinates of the second point;
                <y> is a variable or a parameter (depending on what the input arguments are) where the computed slope values are stored;
    and where the <SUBSET/EXCEPT/FOR qualification> is optional.
Examples:
    LET A = SLOPE(0,0,10,15)
    LET A = SLOPE(X1,Y1,X2,Y2)
Default:
    None
Synonyms:
    None
Related Commands:
    ANGRAD = Return the counter clockwise angle, in radians, of the angle determined by three points.
    DPNTLINE = Compute the perpindicular distance between a point and a line defined by a point and a slope.
    POINTS IN POLYGON = Determine whether points are in the interior of a convex polygon.
    CONVEX HULL = Determine the convex hull of a set of points.
    TRANSFORM POINTS = Perform location, scale, and rotation transformation for a set of points.
    EXTREME POINTS = Determine the extreme points of a set of points.
    LINE INTERSECTIONS = Determine the intersection points for a set of lines.
    PARALLEL LINE = Determine the coordinates for a point that defines a parallel line determined by a point and a line defined by two points.
    PERPINDICULAR LINE = Determine the coordinates for a point that defines a perpindicular line determined by a point and a line defined by two points.
Applications:
    Computational Geometry
Implementation Date:
    2013/01
Program: 
     
skip 25
read convhull.dat x y
.
let y2 x2 = 2d convex hull y x
let xtemp = x2(1)
let ytemp = y2(1)
let y2 = combine y2 ytemp
let x2 = combine x2 xtemp
let x3 = x2
let y3 = y2
let n = size y2
let nm1 = n - 1
retain x2 y2 for i = 1 1 nm1
retain x3 y3 for i = 2 1 n
let slope = slope(x2,y2,x3,y3)
.
set write decimals 4
print x2 y2 x3 y3 slope
    The following output is generated 
     
---------------------------------------------------------------------------
             X2             Y2             X3             Y3          SLOPE
---------------------------------------------------------------------------
         0.0000        -2.0000         1.0000        -1.7300         0.2700
         1.0000        -1.7300         1.7300        -1.0000         1.0000
         1.7300        -1.0000         2.0000         0.0000         3.7037
         2.0000         0.0000         1.7300         1.0000        -3.7037
         1.7300         1.0000         1.0000         1.7300        -1.0000
         1.0000         1.7300         0.0000         2.0000        -0.2700
         0.0000         2.0000        -1.0000         1.7300         0.2700
        -1.0000         1.7300        -1.7300         1.0000         1.0000
        -1.7300         1.0000        -2.0000         0.0000         3.7037
        -2.0000         0.0000        -1.7300        -1.0000        -3.7037
        -1.7300        -1.0000        -1.0000        -1.7300        -1.0000
        -1.0000        -1.7300         0.0000        -2.0000        -0.2700

Date created: 01/23/2013
Last updated: 01/23/2013
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