How to plot the required number of subplots?

As per my script there should be 40 subplots. but I unable tyo recognize the subplots after 28.

Script as as follows:

clc
xs=8;
v=3;
L=20;
ta=0.2;
t=1;
n=1:1:40;
x=0:0.1:20;
position = 0; % position of plot in subplot
fig_num = 1;  % figure() number
for j=1:length(n)
    omga(j)=n(j)*pi*v/L;
    F(j)=exp(-((n(j)*pi*v*ta).^2)/4);
    for i=1:length(x)
        u(i)=sin(n(j)*pi*xs/L)*F(j)*sin(n(j)*pi*x(i)/L)*cos(omga(j)*t);
    end
 position = position + 1;
 if position > 40; position = 1; fig_num = fig_num + 1,end
 figure(fig_num)  
 subplot(10,4,position); 
 plot(x,u)
 axis off
 %plot(x, u)
end

Answer 1

[Chunru]

xs=8;
v=1;
L=20;
ta=0.2;
t=1;
n=1:1:40;
%x=0:0.1:20;
x=0:0.1:60;
position = 0; % position of plot in subplot
fig_num = 1;  % figure() number
u = zeros(size(x));
for j=1:length(n)
    omga(j)=n(j)*pi*v/L;
    F(j)=exp(-((n(j)*pi*v*ta).^2)/4);
    u = u + sin(n(j)*pi*xs/L)*F(j)*sin(n(j)*pi*x/L)*cos(omga(j)*t);
end
plot(x, u)

[Andi]

Thanks, I think something is still missing, as per defination there should be 2 peaks, like the figure below:

[Chunru]

Extend range of x will make multiple peaks. You may need to check the problem formulation.

[Andi]

But as per formulation, the force is exerted at x=8 so, the peak shoudl be at both ends.

Answer 2

[Chunru]

Since you have applied an amplitude factor of something like exp(-n.^2). The amplitude quickly drop to zero at larger iteration.

xs=8;
v=3;
L=20;
ta=0.2;
t=1;
n=1:1:40;
x=0:0.1:20;

position = 0; % position of plot in subplot
fig_num = 1;  % figure() number
for j=1:length(n)
    omga(j)=n(j)*pi*v/L;
    F(j)=exp(-((n(j)*pi*v*ta).^2)/4);
    fprintf('%3d    %20.7g\n', j, F(j));
    for i=1:length(x)
        u(i)=sin(n(j)*pi*xs/L)*F(j)*sin(n(j)*pi*x(i)/L)*cos(omga(j)*t);
    end
 position = position + 1;
 if position > 40; position = 1; fig_num = fig_num + 1,end
 figure(fig_num)  
 subplot(10,4,position); 
 plot(x,u)
 axis off
 %plot(x, u)
end

  1               0.4113691
  2              0.02863695
  3            0.0003373534
  4            6.725225e-07
  5            2.268777e-10
  6             1.29521e-14
  7            1.251273e-19
  8             2.04563e-25
  9            5.659338e-32
 10            2.649521e-39
 11            2.099097e-47
 12             2.81424e-56
 13            6.384883e-66
 14            2.451366e-76
 15            1.592673e-87
 16            1.751091e-99
 17           3.258021e-112
 18           1.025799e-125
 19           5.465557e-140
 20           4.927989e-155
 21           7.519143e-171
 22           1.941469e-187
 23           8.483122e-205
 24           6.272554e-223
 25           7.848677e-242
 26           1.661927e-261
 27           5.955121e-282
 28           3.611043e-303
 29                       0
 30                       0
 31                       0
 32                       0
 33                       0
 34                       0
 35                       0
 36                       0
 37                       0
 38                       0
 39                       0
 40                       0

You can use a smaller value or ta or v in order to see more nonzero plot.

v=0.3;
figure;

position = 0; % position of plot in subplot
fig_num = 1;  % figure() number
for j=1:length(n)
    omga(j)=n(j)*pi*v/L;
    F(j)=exp(-((n(j)*pi*v*ta).^2)/4);
    fprintf('%3d    %20.7g\n', j, F(j));
    for i=1:length(x)
        u(i)=sin(n(j)*pi*xs/L)*F(j)*sin(n(j)*pi*x(i)/L)*cos(omga(j)*t);
    end
 position = position + 1;
 if position > 40; position = 1; fig_num = fig_num + 1,end
 figure(fig_num)  
 subplot(10,4,position); 
 plot(x,u)
 axis off
 %plot(x, u)
end

  1               0.9911567
  2               0.9650932
  3               0.9231682
  4               0.8675151
  5               0.8008624
  6               0.7263123
  7               0.6471032
  8               0.5663805
  9               0.4869985
 10               0.4113691
 11                0.341366
 12               0.2782874
 13                 0.22287
 14               0.1753453
 15               0.1355256
 16               0.1029042
 17              0.07675904
 18              0.05624846
 19              0.04049266
 20              0.02863695
 21              0.01989581
 22              0.01357942
 23             0.009105118
 24             0.005997558
 25             0.003881039
 26              0.00246721
 27             0.001540809
 28            0.0009453145
 29            0.0005697553
 30            0.0003373534
 31            0.0001962304
 32            0.0001121327
 33            6.294814e-05
 34            3.471508e-05
 35             1.88078e-05
 36            1.001019e-05
 37            5.233975e-06
 38            2.688471e-06
 39            1.356637e-06
 40            6.725225e-07

[Andi]

Thanks, I got it. how can I sum multiple u values and then make a singel plot for x,u

[Chunru]

Not sure your question. Can you clarify more?

[Andi]

I want to make a stacked plot by summing all the plots.

u(1)=....

u(2)=...

.

U(40)=...

U(sum)=.... (sum all teh values on index basis)

and then plot (x, u)