Functions only plotting out to x=5

I am attemping to plot 4 scenarios for oscillations, each scenario based on a different value of damping for the system. I think that I have generally accomplished that, but the plots only go out to x=5, and I think it would be helpful to show additional length in the x direction. What would be the best way to do so?

I thought perhaps I should enter "t = 0 : 0.1 : 10" just above the y= and fplot lines near the end of the loop, but received the error:

Error using *

Incorrect dimensions for matrix multiplication. Check that the number of columns in the first matrix matches the number of rows in the second matrix. To perform elementwise multiplication, use '.*'.

syms t C1 C2;
k=4;
m=2;
c_crit=2*sqrt(k*m);
c1=0.99*c_crit;
c2=0.25*c_crit;
c3=0.10*c_crit;
c4=0.02*c_crit;
F0=1;
omeganaught=sqrt(k/m);
omega=1;

for c=[c1 c2 c3 c4]
    % calculate a and b and lambda for each iteration since we know c now
    a=(m*(omeganaught^2-omega^2)/(m^2*(omeganaught^2-omega^2)^2+omega^2*c^2))*F0;
    b=omega*c/(m^2*(omeganaught^2-omega^2)^2+omega^2*c^2)*F0;
    lambda=c/(2*m);
    
    % calculate phi and A now for each iteration now that a and b are known
    A=sqrt(a^2+b^2);
    phi=atan(b/a);
       
    % now that we have phi, A, and lambda, can start solving for C1 and C2
    % using IVs. Formulas for C1 and C2 derived on paper and typed in.
    t=0;
        
    C1=-A*cos(-phi);
    
    C2=lambda*C1+A*sin(-phi);
    
    clear t;
    syms t;
            
    y=exp(-lambda*t)*(C1*cos(omega*t)+C2*sin(omega*t)+A*cos(omega*t-phi));
    fplot(t,y);
  
    hold on;
    
end

axis([0 10 -0.2 0.2])
legend('0.99*c_c_r_i_t','0.25*c_c_r_i_t','0.10*c_c_r_i_t','0.02*c_c_r_i_t');
grid on

Answer 1

[Star Strider]

To plot from 0 to 10, change the fplot call to:

fplot(y,[0 10]);

Then it works without further modification —

syms t C1 C2;
k=4;
m=2;
c_crit=2*sqrt(k*m);
c1=0.99*c_crit;
c2=0.25*c_crit;
c3=0.10*c_crit;
c4=0.02*c_crit;
F0=1;
omeganaught=sqrt(k/m);
omega=1;

figure
for c=[c1 c2 c3 c4]
    % calculate a and b and lambda for each iteration since we know c now
    a=(m*(omeganaught^2-omega^2)/(m^2*(omeganaught^2-omega^2)^2+omega^2*c^2))*F0;
    b=omega*c/(m^2*(omeganaught^2-omega^2)^2+omega^2*c^2)*F0;
    lambda=c/(2*m);
    
    % calculate phi and A now for each iteration now that a and b are known
    A=sqrt(a^2+b^2);
    phi=atan(b/a);
       
    % now that we have phi, A, and lambda, can start solving for C1 and C2
    % using IVs. Formulas for C1 and C2 derived on paper and typed in.
    t=0;
        
    C1=-A*cos(-phi);
    
    C2=lambda*C1+A*sin(-phi);
    
    clear t;
    syms t;
            
    y=exp(-lambda*t)*(C1*cos(omega*t)+C2*sin(omega*t)+A*cos(omega*t-phi));
    fplot(y,[0 10]);
  
    hold on;
    
end

axis([0 10 -0.2 0.2])
legend('0.99*c_c_r_i_t','0.25*c_c_r_i_t','0.10*c_c_r_i_t','0.02*c_c_r_i_t');
grid on

The fplot second argument otherwise defaults to [-5 5].

.

Answer 2

[Paul]

fplot doesn't take t as the first argument as would have to be done for plot. Actually, I guess it can, but it's superfluous. Instead, use a second argument to fplot to indicate the desired plotting interval, as below.

syms t C1 C2;
k=4;
m=2;
c_crit=2*sqrt(k*m);
c1=0.99*c_crit;
c2=0.25*c_crit;
c3=0.10*c_crit;
c4=0.02*c_crit;
F0=1;
omeganaught=sqrt(k/m);
omega=1;
for c=[c1 c2 c3 c4]
    % calculate a and b and lambda for each iteration since we know c now
    a=(m*(omeganaught^2-omega^2)/(m^2*(omeganaught^2-omega^2)^2+omega^2*c^2))*F0;
    b=omega*c/(m^2*(omeganaught^2-omega^2)^2+omega^2*c^2)*F0;
    lambda=c/(2*m);
    
    % calculate phi and A now for each iteration now that a and b are known
    A=sqrt(a^2+b^2);
    phi=atan(b/a);
       
    % now that we have phi, A, and lambda, can start solving for C1 and C2
    % using IVs. Formulas for C1 and C2 derived on paper and typed in.
    t=0;
        
    C1=-A*cos(-phi);
    
    C2=lambda*C1+A*sin(-phi);
    
    clear t;
    syms t;
            
    y=exp(-lambda*t)*(C1*cos(omega*t)+C2*sin(omega*t)+A*cos(omega*t-phi));
%    fplot(t,y);
    fplot(y,[0 25])
  
    hold on;
    
end
%axis([0 10 -0.2 0.2])
legend('0.99*c_c_r_i_t','0.25*c_c_r_i_t','0.10*c_c_r_i_t','0.02*c_c_r_i_t');
grid on