how can i plot this equation ??? please

clear all
clc
%le 29/10/2013 à 23h00
%les géométries de la poutre
M=30; % masse de la poutre KG/ML??
EI=200*10^7;% Rigidité flexionnelle de la poutre N/m^2
%l=22;%m

%les caractéristiques du sol
c=0;% constante d'amortissement
k=0.2*10^8;% rigidité du sol N/m^2
v=5;%vitesse m/s de chargement
n1=5;%nombre des modes

%longueur de la poutre en m
l=(3*pi/2)*(4*EI/k)^0.25; %m; 

%les conditions initiales
v_0=0;%m/s;vitesse initiale
T_0=0.01*10^-4;%m déplacement initial
t1=l/v;

for m=1:n1;
  x=1:0.01:l+1;
  phi(x,m)=sin((x-1)*pi*m/l);
  t=1:0.01/v:t1;
  beta=c/(2*M);
  B=T_0;
  w_d(m)=((((m^4)*(pi^4)*EI)/(M*(l^4)))+(k/M))^0.5; %pulsation propre
  w_n(m)=((w_d(m)^2)-(beta^2))^0.5;% pseudo pulsation
  A(m)=((v_0)+(B*beta))/w_n(m);
  T(t,m)=(exp(-beta*(t-1)*(A(m)*sin((w_n(m))*(t-1))+B*cos((w_n(m))*(t-1)))));
  ww(x,t,m)=phi(x,m)*T(t,m);%(sin(m*pi*(xx1(i)-1)/l))* T(j,m);%((exp(-beta*(tt1(j)-1)))*(A(m)*sin((w_n(m))*(tt1(j)-1))+B*cos((w_n(m))*(tt1(j)-1))));
end

 x=1:0.01:l+1;
    t=1:0.01/v:t1;
        ww1(x,t)=0;
        for m=1:n1;
            ww1(x,t)=ww1(x,t)+ww(x,t,m); 
        end

plot (ww1(:,1),'B');
hold on
%remarque : se sont des ondes stationaires changent d'emplitudes mais ne
%changent pas de position.

[Walter Roberson]

Side note: you can replace

          ww1(x,t)=0;
          for m=1:n1;
            ww1(x,t)=ww1(x,t)+ww(x,t,m); 
          end

with

          ww1(x,t) = sum(ww(x,t,:));

[sihem chaib]

ok think you i try your proposition

Answer 1

[Walter Roberson]

Your code has

t=1:0.01/v:t1;
ww1(x,t)=0;

so you are trying to use t as an index into an array. But t has values like 1.80 and floating point numbers cannot be used as indices.

Try

t=1:0.01/v:t1;
ww1(x, 1:length(t)) = 0;

Except, that is, that as I noted above you do not need to initialize ww1(x,t). So you can take the statement I gave

ww1(x,t) = sum(ww(x,t,:));

and replace it with

ww1(x,1:length(t)) = sum(ww(x,1:length(t),:),3);