how do I make a for loop

Hi ,

i want to code some equation to calculate displacement , velocity and acceleration but the thing is that I need to use a for loop to calculate many times and the equation used in calculations depend on the output and my first out put must be zero I can't solve this problem

% response spectrum

% response spectrum

[kobe]=xlsread("Kobe.xlsx.xlsx")
[dt]=kobe(:,1);
[E ]=kobe (:,2);
[T ]= (0.1:0.02:8);
M = 4./(dt).^2
N = 4*pi^2 ./(T).^2;
H= 8*pi*0.05./(T);

  
      
    
    for j = 1:length(T)
    [T ]= (0.1:0.02:8);

    dis = dis(j);
    vel = vel(j);
    acc = acc(j);
    if (j)==1
        dis = 0;     % the first input
        vel = 0;     % the first input
        acc = 0;     % the first input
    end
  delta_dis = - (E) + M * vel +2* acc +H * vel / N + H ./(dt) + M;
  delta_vel = 2./(dt) * delta_dis - 2* vel;
  delta_acc = (delta_dis - vel.*(dt))*4./(dt).^2 - 2 *acc;
    
        
    
   
 dis = dis +delta_dis; % after the first loop the new value for dis,vel and acc               
 vel = vel + delta_vel; % and I need to put this new value in the loop 
 acc = acc + delta_acc;
   
    end
        
 figure (1) ;         % i want to plot the maximum values 
    
subplot (3,1,1);
plot (T , max(dis));
subplot (3,1.2);
plot (T , max(vel));
subplot (3,1,3);
plot (T , max(acc));

[Image Analyst]

People are probably waiting for you to attach the "Kobe.xlsx.xlsx" that you forgot to attach.

Also, type control-a, control-i in MATLAB before you paste it here so that the indenting will be correct.

Answer 1

[Jan]

You are mixing the values of the former step, the current step and the vector of outputs. Without clear comments or an exhaustive explanation of what you want to do, it is not possible to guess the intention of the code reliably. Some guessing:

kobe=xlsread("Kobe.xlsx.xlsx")
dt= kobe(:,1);
E = kobe(:,2);
T = 0.1:0.02:8;
M = 4 ./ dt.^2
N = 4 * pi^2 ./ T.^2;
H = 8 * pi * 0.05 ./ T;

dis = 0;     % Initial value?
vel = 0;     % Initial value?
acc = 0;     % Initial value?

% Maybe:
disOut = zeros(1, length(T));
velOut = zeros(1, length(T));
accOut = zeros(1, length(T));

for j = 1:length(T)
   %  dis = dis(j);  % This has not been defined before?
   %  vel = vel(j);
   %  acc = acc(j);

   delta_dis = -E + M * vel + 2 * acc + H * vel / N + H ./ dt(j) + M;
     % Sure that you mean delta_dis in these two lines?
   delta_vel = 2 ./ dt * delta_dis - 2 * vel;
   delta_acc = (delta_dis - vel * dt(j)) * 4 ./ dt(j) .^ 2 - 2 * acc;
   
   dis = dis + delta_dis;  % after the first loop the new value for dis,vel and acc               
   vel = vel + delta_vel;  % and I need to put this new value in the loop 
   acc = acc + delta_acc;
   
   disOut(j) = dis;
   velOut(j) = vel;
   accOut(j) = acc;
end

[Abed Eltablawy]

ok I will explain in more details .

I have variable (T= 0.1:0.02:8) and i have data for dt and E for each number of T I need to compute 3 variables dis,vel and acc. i will have too meny values for each of them so , I will pick the max for each value of T and the three variables

doing this for each no. of T and plot graphs between T and maxdis , T and maxvel , T and maxacc

[Abed Eltablawy]

thank you for answers I really appriciate that