Error using * Inner matrix dimensions must agree.

Hello, im trying to figure out what is the problem (Error in ArduinoComunication v3(i)=v3(1:i)+((v1(1:i)+v1(1:(i-1)))/2)*(x(1:i)-x(1:(i-1))); ), my 2 vectors have the same size. here is part of the code

    v1 = zeros(1,tmax*rate);
    v2 = zeros(1,tmax*rate);
    v3 = zeros(1,tmax*rate);
    while t<tmax
    t = toc;
    % leer del puerto serie
    a = fscanf(s,'%f,%f')';
    v1(i)=a(1);
    v2(i)=a(2);
    v3(i)=v3(1:i)+((v1(1:i)+v1(1:(i-1)))/2)*(x(1:i)-x(1:(i-1)));

    % dibujar en la figura
    x = linspace(0,i/rate,i);
    % velocity
    set(l1,'YData',v1(1:i),'XData',x);
    set(l2,'YData',v2(1:i),'XData',x);
    %set(l3,'YData',v3(1:i),'XData',x);

    drawnow
    % seguir
    i = i+1;
end % code

can you guys tell me what im doing wrong thanks

[John Chilleri]

It looks like you mean,

v3(i)=v3(1,i)+((v1(1,i)+v1(1,(i-1)))/2)*(x(1,i)-x(1,(i-1)));

Instead of,

v3(i)=v3(1:i)+((v1(1:i)+v1(1:(i-1)))/2)*(x(1:i)-x(1:(i-1)));

So perhaps you've placed : where you should have placed ,?

Hope this helps!

[John Chilleri]

If that's not the mistake, then there are some problems, as you are trying to multiply a row vector by a row vector, which is not possible (unless you want element-wise, in which case you should use .* rather than *). Additionally, you seem to be subtracting/adding two vectors of different lengths, twice. That is, x(1:i)+x(1:(i-1)) are two vectors of different length that can't be subtracted, you do this similarly with v1.

Good luck!

[John Prada]

woow, thank you Now i got this error

Subscript indices must either be real positive integers or logicals.

Error in ArduinoComunication v3(i)=v3(1,i)+((v1(1,i)+v1(1,(i-1)))/2)*(x(1,i)-x(1,(i-1)));

my indices are supposed to be integers

[John Chilleri]

I would guess that you have i = 1 to start off, and when it tries to access v1(1,(i-1)) it's attempting to access v1(1,0) which is not an element. This will also be true for the x(1,(i-1)) line.

You'll need to either skip i=1 or figure out how to handle that case!

[John Prada]

well the thing is that im trying to get velocity data from accelerometer (real time), v1(i)=a(1); its the acceleromter data so in 'v3', im trying to do something like this

// velocity

vx = vx+ ((ax + ax0)/2) * (t - t0);

Am i wrong ?

[John Chilleri]

I would start with i=2 and place your initial conditions in v1(1),v2(1),v3(1) - these might be zero if you're starting with no movement.

[John Prada]

v1 = zeros(1,tmax*rate);
v2 = zeros(1,tmax*rate);
v3 = zeros(1,tmax*rate);
x= zeros(1,tmax*rate);
i = 2;
t = 0;
% ejecutar bucle cronometrado
tic
while t<tmax
  t = toc;
  % leer del puerto serie
  a = fscanf(s,'%f,%f')';
  v1(i)=a(1);
  v2(i)=a(2);
  v3(i)=v3(1,i)+((v1(1,i)+v1(1,(i-1)))/2)*(x(1,i)-x(1,(i-1)));
  % dibujar en la figura
  x = linspace(0,i/rate,i);
  % velocity
  set(l1,'YData',v1(1:i),'XData',x);
  set(l2,'YData',v2(1:i),'XData',x);
  %set(l3,'YData',v3(1:i),'XData',x);

    drawnow
    % seguir
    i = i+1;
end

still having error

Index exceeds matrix dimensions.

Error in ArduinoComunication (line 47) v3(i)=v3(1,i)+((v1(1,i)+v1(1,(i-1)))/2)*(x(1,i)-x(1,(i-1)));

[John Chilleri]

It looks like your i can grow larger than tmax*rate, which is the length of your v1. Accessing v3(i) when i is larger than tmax*rate can cause this error.

I would try deleting the v3(1,i) at the beginning of that line as it doesn't really contribute anything since v3(1,i) was initialized to 0.

[John Prada]

thanks, i did what you said and i changed some parts from my code. this is the new code

   v1 = zeros(1,tmax*rate);
v2 = zeros(1,tmax*rate);
v3 = zeros(1,tmax*rate);
i = 2;
t = 0;
% ejecutar bucle cronometrado
tic
while t<tmax
    t = toc;
    % leer del puerto serie
    a = fscanf(s,'%f,%f')';
    v1(i)=a(1);
    v2(i)=a(2);
    % dibujar en la figura
    x = linspace(0,i/rate,i);
    v3(i)=((v1(1,i)+v1(1,(i-1)))/2)*(x(1,i)-x(1,(i-1)));

    % velocity
    set(l1,'YData',v1(1:i),'XData',x);
    set(l2,'YData',v2(1:i),'XData',x);
    %set(l3,'YData',v3(1:i),'XData',x);

    drawnow
    % seguir
    i = i+1;
end % code

[John Chilleri]

I hope it's working and producing good results!

Good luck!