How can I plot an equation that includes sigma?

I'm trying to plot the eqution above and I used symsum but the code below plots nothing. How can I fix this?(N_k is the )

clear

clc

%Parameter

L_c=0.05;%m

zeta=1/29;

V_avg=11.2;%m/s

St=0.29;

d=0.025;%m

Cir_0=d/(2*St);%m

Cir_cr=Cir_0*V_avg;

B_0=0.006;%s/m^2

c=700;%m/s

P_avg=101325;%Pa

gamma=1.4;

omega=250;

omega_d=sqrt(4*omega^2-zeta^2);

B=B_0*Cir_cr*omega*cos(omega*L_c/c);

%calculation

t_upTo=1.5;

t_step=0.01;

t_j=0.04;

for t=0:t_step:t_upTo

N_k=floor(t/t_j);

syms k

total=B/omega_d.*symsum(exp(-(zeta/2).*(t-t_j*k)).*(-zeta.*sin(omega_d/2.*(t-t_j*k))+omega_d.*cos(omega_d/2.*(t-t_j*k))),k,0,N_k);

plot(t,total)

end

Answer 1

[Star Strider]

I changed ‘t’ to ‘tv’ and then created ‘t’ in each iteration as ‘tv(k1)’ to produce a vector for ‘total’ that is then plotted at the end.

Try this —

%Parameter
L_c=0.05;%m
zeta=1/29;
V_avg=11.2;%m/s
St=0.29;
d=0.025;%m
Cir_0=d/(2*St);%m
Cir_cr=Cir_0*V_avg;
B_0=0.006;%s/m^2
c=700;%m/s
P_avg=101325;%Pa
gamma=1.4;
omega=250;
omega_d=sqrt(4*omega^2-zeta^2);
B=B_0*Cir_cr*omega*cos(omega*L_c/c);
%calculation
t_upTo=1.5;
t_step=0.01;
t_j=0.04;
tv=0:t_step:t_upTo;
for k1 = 1:numel(tv);
    t = tv(k1);
    N_k=floor(t/t_j);
    syms  k 
    total = B/omega_d.*symsum(exp(-(zeta/2).*(t-t_j*k)).*(-zeta.*sin(omega_d/2.*(t-t_j*k))+omega_d.*cos(omega_d/2.*(t-t_j*k))),k,0,N_k); 
    totalv(k1) = double(total);
end

figure
plot(tv,totalv)
grid
xlabel('t')
ylabel('total')

The original plot call did not work first because ‘total’ is a symbolic variable, not a numeric variable. Even if it had been a numeric variable, plot would not have plotted anythinbg because it only plots lines between two or more defined points, not single points, unless it was told to plot with a marker. This slight variation on your original code solves both of those problems.

.

[Sojung Park]

I didn't know about the difference of symbolic and numeric variable. This was very helpful. Thanks a lot!

[Star Strider]

As always, my pleasure!