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modeling a mathematical shape 
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Frank98
Newbie Joined: 15.Feb.2017 Location: Bahamas Using: autocad 2015 Status: Offline Points: 4 
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Posted: 15.Feb.2017 at 21:28 
how can i model such a plot in autocad.
this plot what created using a mathematical formula ,demostrated in mathlab. thanks


Kent Cooper
Senior Member Joined: 12.Mar.2013 Location: United States Using: AutoCAD, Architectural Desktop Status: Online Points: 305 
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The equations would be necessary....
That looks like some kind [two kinds, really] of formula in which the angle to a point on the curve is based on the inverse of a trigonometric function whose value swings between positive and negative without ever going to infinity [such as sine or cosine], applied to some multiplier of the local radius, and for the browner curve with a constant angle [looks like 45 degrees] added to the result. That shouldn't be very hard to work out  for a related routine that draws polynomial functions [y = ax^n + bx^(n1) + .... + px^2 + qx + r], see my PolynomialFunction.lsp routine, available here. But this one, being radial, would not involve X and Y coordinates, but instead (polar) functions measured from the origin as basepoint, in a (repeat) function stepping through small increments of radius as the distance arguments, and calculating the angle arguments for each based on the equation, and presumably used in a SPLINE, or perhaps a POLYLINE that you could splinecurve to smooth it out.


Vladimir Michl
Moderator Group CAD Studio a.s. Joined: 26.Jul.2007 Location: Czech Republic Using: Autodesk software Status: Offline Points: 1668 
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You can use our 2DPLOT utility (see http://www.cadstudio.cz/en/apps/2dplot/). You equation then should be expressed in cartesian space (X/Y):
; for range (01.5> (defun fPolar1 (u / r tau alfa R0) ;x = (* r (cos th)) ;y = (* r (sin th)) (setq r u) (setq tau 1.1) ; example (setq alfa 1.0) ; example (setq R0 0.1) ; example (setq th (* alfa (sin (/ (* pi (log (/ r R0))) (log tau))))) ; your expression (list (* r (cos th)) (* r (sin th))) ; return (X Y) ) Then call: (2Dplot fPolar1 0.001 1.5 0.001) meaning  draw my function "fPolar1" from 0.001 to 1.5 (the radius), with ministeps of 0.001 

Kent Cooper
Senior Member Joined: 12.Mar.2013 Location: United States Using: AutoCAD, Architectural Desktop Status: Online Points: 305 
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Another, (polar)based, solution (along with Vladimir's solution above) is over here. See also other Posts in that same thread.
EDIT: That link doesn't seem to work. Try copy/pasting this: https://forums.autodesk.com/t5/autocad20132014201520162017/modelingamathematicalshape/mp/6886507#M163554 Edited by Kent Cooper  17.Feb.2017 at 21:02 

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