plotting simple symbolic equation

Question

Sean Smith 2011-11-11

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https://ww2.mathworks.cn/matlabcentral/answers/21015-plotting-simple-symbolic-equation

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]);

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Answer 1

bym 2011-11-11

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https://ww2.mathworks.cn/matlabcentral/answers/21015-plotting-simple-symbolic-equation#answer_27731

在 MATLAB Online 中打开

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