need codes to find equation of straight line y = mx + b

[Michael Mattias]

Time for one of my favorite sayings.

Computers don't do the math. People do the math.
Computers do the arithmetic.

The Math here is to simply solve the simutaneous equations

Y1 = mX1 + c
Y2 = mX2 + c

.. for m and c.

[Dale Yarker]

delete 2 CONSOLE SET lines
Add LOCAL InStr AS STRING
Change exit loop to -
InStr = GRAPHIC$(INKEY$)
if InStr = $ESC THEN EXIT DO
LOOP

[Tim Lakinir]

Thank you Sir Mark, can you please make the code in PBWin10 as I don't have PBCC?

[Dale Yarker]

Why GRAPHIC REDRAW? GRAPHIC ATTACH does not have REDRAW option.

Cheers,

[Mike Doty]

Mark,
GoTo GRD not found

[Mike Doty]

Mark gives a solution.
Might visually test your points on a line using \samples\ddt\graphic\PwrClock\PwrClock.bas

[Mark Hunter]

Tim,

Function PBMain
 Local x1, y1, x2, y2 As Single   'two particular points
 Local winC As Dword              'graphic window handle
 Local x As Single, y As Single   'general point on line

' find
 Local m As Single    'slope
 Local b As Single    'y intercept

 ' Setup graphic window, give console focus so catches keystrokes
 Graphic Window "", 0, 0, 800, 800 To winC
  Graphic Attach winC, 0, ReDraw
 Graphic Scale (-400,400)-(400,-400)       'top window uses -241, bottom 249
 Console Set Loc 850, 0
 Console Set Focus

 Do

  Graphic Clear

  'random pairs of points
  x1 = 100 * Rnd - 100 : y1 = 100 * Rnd - 100
  x2 = 100 * Rnd - 100 : y2 = 100 * Rnd - 100

  ' Check if line is vertical (slope infinite)
  If x1 = x2 Then
   For y = -300 To 300
    Graphic Set Pixel(x1, y), %Black
   Next
   GoTo GRD
  End If

  m = (y2 - y1) / (x2 - x1)

  ' Now we know the m in
  '   y = mx + b
  ' To find b, plug in one of the points, say (x1, y1), and solve for b
  b = y1 - m * x1

  ' Draw the line
  For x = -300 To 300
   y = m * x + b
   Graphic Set Pixel(x, y), %Black
  Next

GRD:
  ' Empahsize two give points
  x = x1 : y = y1
  Graphic Ellipse (x - 2, y - 2) - (x + 3, y + 3), %Red, %Red
  x = x2 : y = y2
  Graphic Ellipse (x - 2, y - 2) - (x + 3, y + 3), %Red, %Red

  Graphic ReDraw

 Loop Until WaitKey$ = $Esc

End Function

[Gary Beene]

Howdy, Tim!

This page explains the steps ...

https://www.mathsisfun.com/algebra/line-equation-2points.html

[Tim Lakinir]

Hi everyone

Are there any codes available in this forum to get a linear equation y= mx + b when given 2 points (x1,y1) and (x2,y2) ?
and to determine whether a third point (x3, y3) lies on this line ?

I'm not too well educated thus I need to catch up.