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====== Differences ====== This shows you the differences between two versions of the page.

--- gibson:teaching:fall-2013:math445:lab11 [2013/12/05 08:35]
szeto
+++ gibson:teaching:fall-2013:math445:lab11 [2013/12/05 09:10] (current)
szeto
@@ Line 45: / Line 45: @@
 g = 9.81;        % m/s^2, acceleration due to gravity
 .
+.
+.
 f = @(t,x) [ ....];
-.
-[t,x]= ode45(f, ...   [ 0,0,v0*cos(theta), v0*sin(theta) );
+[t,x]= ode45(f,[0:0.1:200] ,[ 0,0,v0*cos(theta), v0*sin(theta) );
+xdistance = interp1(x(50:end,2), x(50:end,1), 0);  % This is how you can compute ''xdistance''
+% accurately from an ''x,y'' trajectory using interpolation.
+% It will return the value of $x$ for which $y=0$, i.e.
+% where the cannonball hits the ground.
 end
 </code>
-Do plotting and interpolating in another script or on the command line.
-You can compute ''xdistance'' accurately from an ''x,y'' trajectory using interpolation:
+Once your function works, play around with the parameters ''v0, theta'' to answer the questions.
+On the command line, you can USE this function like this.
+<code>
+  xdistance = projectile(100,pi/2)
+  xdistance = projectile(100,pi/4)
+  xdistance = projectile(100,pi/8)
+</code>
-  xdistance = interpolate(x(50:end,2), x(50:end,1), 0);
+If your xdistance is a NaN, you may have to increase the number 50 in the interp1 function (1000 might be good, that is roughly half the length of [0:0.1:200]).
-That will return the value of $x$ for which $y=0$, i.e. where the cannonball hits the ground. Once your function works, play around with the parameters ''v0, theta'' to answer the questions.

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