Error using plot Conversion to double from sym is not possible.

plot([0,2],[0,0],'k');             
plot([0,0],[0,2],'k');              
sol=dsolve('D3y-3*D2y+y=-3*x','y(0)=0','Dy(0)=3','D2y(0)=0','x');                                       
xx = 0:0.1:2;                          
yy = subs(sol,'t',xx);            
plot(xx,yy);
axis([-1,2.5,-1,2.5]);

Answer 1

[Walter Roberson]

plot(xx, double(yy))

If that gets you the same error then examine sol and you will likely find that it has at least one free variable other than t.

[Gandi Pirkov]

Error using mupadmex Error in MuPAD command: DOUBLE cannot convert the input expression into a double array.

If the input expression contains a symbolic variable, use the VPA function instead.

Error in sym/double (line 936) Xstr = mupadmex('symobj::double', S.s, 0);

Error in zad1 (line 8) plot(xx, double(yy));

I got this :(

[Walter Roberson]

That indicates that your dsolve() result has at least one free variable beyond the 't' that you substituted in. "A"'s response pointing out that you would likely not have a "t" looks reasonable to me.

Answer 2

[A]

Dear Gandi Pirkov,

the variable of your equation is x, why you are addressing t and xx?! I have modefied it, the following code works without error

plot([0,2],[0,0],'k'); plot([0,0],[0,2],'k');

sol=dsolve('D3y-3*D2y+y=-3*x','y(0)=0','Dy(0)=3','D2y(0)=0','x'); x = 0:0.1:2;

plot(x,subs(sol));

axis([-1,2.5,-1,2.5]);

Good Luck

Answer 3

[omayma mansouri]

Error using plot Conversion to double from sym is not possible. need help to solve this problem, thank you

[omayma mansouri]

Error using plot Conversion to double from sym is not possible need help to solve this problem, thank you my code matlab

Answer 4

[Steven Lord]

Change your SUBS call to substitute xx in for x not t, since you told DSOLVE that your independent variable is x by specifying it as the final input argument.

 yy = subs(sol, 'x', xx);