MATLAB: How to use ode45 with input vector

MATLABode45springvector input

I'm modeling a system mass spring damper and i have aceleration signal with 20200 values. Im testing with the 3 first values (-0.0120 ; -0.015 ; -0.0109) but ode45 is just using the value -0.0120. What can i do to use these 3 values ?
 %MODELING NON-INERTIAL SYSTEM OF 2nd ORDER
 % M x''(t) + b x'(t)+ k x(t) = f(t) 
 %acx = a(:,1)';
 acx = [-0.0120 ; -0.015 ; -0.0109 ]';
 cond.ini = [0 0];
 [t, x] = ode45(@daceler, t, cond.ini, [] , acx);
 plot(t,x);
 function  f = daceler(~,x,acx)
 f = zeros (2,1); 
 b=0.01; 
 k=0.18; 
 m=0.005; 
 i = length (3);
 f(1)=x(2); 
 f(2)=-(b/m)*x(2)-(k/m)*x(1)+((1/m)*acx(1:i)); 
 end

Best Answer

You have
i = length (3);
length(3) is length of the 1 x 1 array whose numeric value is 3, and that length is 1, so i will be assigned one, and then acx(1:i) will be acx(1:1)
If you were to change that to something like
i = length(acx)
then you would be computing a vector of values on the right side of the f(2) assignment, which would be a problem because the storage location f(2) only has room for one value.
Note: you are relying upon a syntax for ode45 that has not been documented in over a decade. You should parameterize the function instead.
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