Why does it say f plot error line 97

I have the equation from ysol is 3*cos(2*x) - 3*exp(-3*x) - 2*sin(2*x) however whenever i plot it using fplot it gives me an error Index exceeds matrix dimensions.

Error in fplot (line 97) xmin = min(lims(1:2)); xmax = max(lims(1:2));

Heres my codes

ySol(x) = dsolve(ode,conds)

ySol = simplify(ySol);

x = 0.0:1.:30.0;

figure

fplot(ySol,'r',[0 30])

Answer 1

[Star Strider]

Since ‘x’ is the independent variable in your equation, do not define it as a vector if you want to use the fplot function. Leave it undefined, and fplot will implicitly consider ‘ySol’ as a single-variable function.

This works:

ySol = 3*cos(2*x) - 3*exp(-3*x) - 2*sin(2*x);

figure
fplot(ySol,'r',[0 30])

[Maria De Silva]

It still gives me the same error.

ySol(x) = dsolve(ode,conds); ySol = simplify(ySol);

figure fplot(ySol,'r',[0 30])

[Star Strider]

The code I posted works correctly.

What is your original differential equation?

Please post all your code. I cannot determine where the problem begins without seeing everything you did.

[Maria De Silva]

syms y(x)
Dy = diff(y);
Dy2= diff(y,2);
ode = diff(y,x,3)+3*diff(y,x,2)+4*diff(y,x,1)+12*y == 0;
cond1 = y(0) == 0;
cond2 = Dy(0) == 5;
cond3 = Dy2(0) == -39;
conds = [cond1 cond2 cond3];
ySol(x) = dsolve(ode,conds);
ySol = simplify(ySol)

figure
fplot(ySol,'r',[0 30])

title(' Homogeneous linear ODE, complex roots, IVP')
legend('3*cos(2*x) - 3*exp(-3*x) - 2*sin(2*x)')

Here is everything

[Star Strider]

Your code as you posted it works perfectly for me and produces this plot (in R2017a):