How can I fix this error?

Hello, I wrote this code:

figure(3)
dt = 0.001;
T = 60;
t = [0:dt:T] ;
omega0 = 2 * pi / T;
for k = 1:20
    ck = cos (k * omega0 * t); % cosine component
    a(k) = 2/T * ( sum (ECG_ac.*ck) * dt);
    sk = sin (k * omega0 * t); % sine component
    b(k) = 2/T * ( sum (ECG_ac.*sk) * dt);
end
magnitude = sqrt(a.^2 + b.^2);
plot(magnitude)

but i have this error:

Error using  .* 
Matrix dimensions must agree.

Error in Q2ECG (line 40)
    a(k) = 2/T * ( sum (ck.*ECG_ac) * dt);

what's wrong?

Thanks for your help

Answer 1

[Roger Stafford]

Judging by your error message, the two arrays, ck and ECG_ac, have different sizes. That's a no-no.

[Walter Roberson]

We do not know what size ECG_ac is, but ck is the same size as t

[Ghazal Hnr]

The size of ECG_ac is [1 15000], Is anyway to fix this?

[Roger Stafford]

Just change dt:

dt = linspace(0,T,15000);

[Ghazal Hnr]

I have the same error again!

Answer 2

[Walter Roberson]

T = 60;
t = linspace(0,T,length(ECG_ac));
dt = t(2)-t(1);
omega0 = 2 * pi / T;
for k = 1:20
    ck = cos (k * omega0 * t); % cosine component
    a(k) = 2/T * ( sum (ECG_ac.*ck) * dt);
    sk = sin (k * omega0 * t); % sine component
    b(k) = 2/T * ( sum (ECG_ac.*sk) * dt);
end
magnitude = sqrt(a.^2 + b.^2);
plot(magnitude)