How to plot polynomial function correctly?

94 vues (au cours des 30 derniers jours)
Adrian Brand
Adrian Brand le 24 Mar 2020
Hello, I'm trying to plot polynomial function but output is always bad. Can you help me find, what I'm missing? Thank you.
This is my code:
d = @(g)1-5*g-2.5*g.^2+6*g.^3+5*g.^4;
e = -2:1/100:2;
plot(e,d(e));
This is what I'm getting:
And this is what I want:

Réponse acceptée

Alex Mcaulley
Alex Mcaulley le 24 Mar 2020
Your code is working fine, the difference is just the axis limits. Try this:
d = @(g)1-5*g-2.5*g.^2+6*g.^3+5*g.^4;
e = -2:1/100:2;
plot(e,d(e));
ylim([-2,5])
xlim([-3,6])

Plus de réponses (1)

John D'Errico
John D'Errico le 24 Mar 2020
Modifié(e) : John D'Errico le 24 Mar 2020
Hmm. Why does this feel like deja vu? (Answer: I just answered almost the same question for someone else, not 5 minutes ago.)
d = @(g)1-5*g-2.5*g.^2+6*g.^3+5*g.^4;
e = -2:1/100:2;
plot(e,d(e));
grid on
It looks fine to me. Whats the problem? That two programs arbitrarily chose a different set of axes to plot the same curve?
axis([-3,4.5,-1.5,4.5])
Same curve. Same plot. Very different conclusions, just by changing the axis scaling.
  2 commentaires
Adrian Brand
Adrian Brand le 24 Mar 2020
thank you very much too.
María Guadalupe Gama Cruz
María Guadalupe Gama Cruz le 24 Fév 2021
how do you plot the x axis?

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