ezplot is plotting a blank plot

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Brenda Galabe
Brenda Galabe 2018-12-12
编辑： Cris LaPierre 2018-12-12
no errors nut plot is blank
syms y(x)
a=2;
b=6;
c=1;
d= 8;
e = 6;
ode = diff(y,x) == (-d*x)/(e*y);
ysol = vpa(dsolve(ode))
ezplot(ysol(1))
hold on
ezplot(ysol(2))

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回答（3 个）

Mark Sherstan
Mark Sherstan 2018-12-12
You need to solve for your constant C2 otherwise your function is no longer in terms of just x which is a requirment of ezplot.
  2 个评论
Brenda Galabe
Brenda Galabe 2018-12-12
THIS EQUATION DID PLOT AND IT HAD CONSTANTS TOO, whats the difference between the tw0
syms y(x)
a=2;
b=6;
c=1;
ode = diff(y,x) == (a*x*y)/(b*x^2-c*y^2);
ysol = vpa(dsolve(ode))
ezplot(ysol(1))
hold on
ezplot(ysol(2))
ezplot(ysol(3)
Cris LaPierre
Cris LaPierre 2018-12-12
编辑：Cris LaPierre 2018-12-12
You did not try to plot the solution that contains constant C5 (ysol(4)). Your plots are for
  • 0
  • 2x
  • -2x

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Cris LaPierre
Cris LaPierre 2018-12-12
编辑：Cris LaPierre 2018-12-12
You equation has two variables. You need to provide a value for for ezplot to be able to plot the functions.
Also, best to heed the warnings in the documentation - use fplot instead of ezplot.
If I use fplot and substitute in a value for C2, your code works.
...
ysol = subs(ysol,'C2',25)
fplot(ysol(1))
hold on
fplot(ysol(2))
Brenda Galabe
Brenda Galabe 2018-12-12
this error happens instead
Index exceeds matrix dimensions.
Error in fplot (line 56)
lims = args{2};
  1 个评论
Cris LaPierre
Cris LaPierre 2018-12-12
I didn't realize you were using an older version of MATLAB. The behavior will be different. Use ezplot for now.

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