plotting simple symbolic equation

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Sean Smith
Sean Smith on 11 Nov 2011
I'm new to using symbolic equations and variables. I am trying to plot this symbolic equation but I keep getting an error saying Maximum recursion limit of 500 reached. also when I type h into matlab to see the equation it shows the first value -0.12 as - 0.12000000000080035533756017684937 I don't get why it does this and it just does it to that coefficient. And the g value has an obnoxious amount of decimal places and I'm using format short. It's a trajectory equation, so g is when the ball hits the ground.
syms t
h=sym('-0.12*t^4+12*t^3-380*t^2+4100*t+220');
g=solve('-0.12*t^4+12*t^3-380*t^2+4100*t+220=0');
g=g(2) %only answer that makes sense
figure; ezplot(h,[0,g]);

Answers (1)

bym
bym on 11 Nov 2011
where to begin...
first since you have declared t to be symbolic, you can define your equation to be
eq = -0.12*t^4+12*t^3-380*t^2+4100*t+220 % no quotes
sol = solve(eq) % solve the equation matlab assumes it's =0
vsol = vpa(sol,5) % takes care of your 'obnoxious' decimal places
ezplot(char(eq),[0 max]) % plot function - note conversion of symbolic to character

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