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From: Bob felleo on 10 Jul 2010 05:47
i have a program that shows floating redballs i need a matlab program that would include gravity in this if you could change it to be the apportion answer i would be very great full

%redball.m
classdef redball < handle
properties
x; % x position
y; % y position
vx; % velocity in x
vy; % velocity in y
r; % radius
end
properties(Constant)
minx = -10;
maxx = 10;
miny = -10;
maxy = 10;
end

methods
function obj = redball( )
obj.x = 18*rand(1) - 9;
obj.y = 18*rand(1) - 9;
obj.vx = .9*rand(1)-.45;
obj.vy = .9*rand(1)-.45;
obj.r = rand(1)*.9 + .1;
end
function [xpts ypts] = getpts(obj)
t = 0:0.1:(2*pi);
xpts = obj.r*cos(t) + obj.x;
ypts = obj.r*sin(t) + obj.y;
end
function obj = move(obj)
obj.x = obj.x + obj.vx;
if((obj.x-obj.r)<=obj.minx | (obj.x+obj.r)>=obj.maxx);
obj.vx = -1*obj.vx;
if(obj.x<0)
obj.x = -9.99+obj.r;
else
obj.x = 9.99-obj.r;
end
end
obj.y = obj.y + obj.vy;
if((obj.y-obj.r)<=obj.miny | (obj.y + obj.r)>=obj.maxy);
obj.vy = -1*obj.vy;
if(obj.y<0)
obj.y = -9.99+obj.r;
else
obj.y = 9.99-obj.r;
end
end
end
end
end

%redball2.m
clear
clear
clc
for j = 1:40
v(j) = redball;
end

while(1)
hold on;
for j = 1:40
v(j).move;
[xp yp] = v(j).getpts;
plot(xp,yp,'ro');
axis([-10 10 -10 10])
end
pause(.01)
hold off;
plot([0],[0]);
end
From: John D'Errico on 10 Jul 2010 06:30
"Bob felleo" <bobbyfelleo(a)yahoo.com> wrote in message <i19fio$1to$1(a)fred.mathworks.com>...
> i have a program that shows floating redballs i need a matlab program that would include gravity in this if you could change it to be the apportion answer i would be very great full
>
> %redball.m
> classdef redball < handle
....

Sigh. That would involve significantly rewriting your
code. But it is your homework assignment to do
after all.

Perhaps you should think about how gravity acts.
Or perhaps you should look at how the several
codes were written on the file exchange that model
a ball that falls under the force of a gravitational
field.

Finally, I will point out that in real life when you
write code, it is a good thing to use comments!

Code that has no comments explaining what each
block of code does can be virtually impossible to
decode. In fact, my recommendation is a comment
for EVERY line of code. At the least, provide a
comment for every code fragment, perhaps every
block of 3-5 lines. Explain the purpose of that
code fragment to follow, how it works.

This way, when you get run over by a bus, and
your colleagues are forced to maintain your legacy
of code, they will not curse your bones every time
they are forced to look at your code.

John
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