Index exceeds array bounds.

for k=3:Ns

% 1st derivative

ikd=(it(k+1)-it(k-1))/(2*h);

% 2nd derivative

ikdd=(it(k+1)-2*it(k)+it(k-1))/(h^2);

% Peak current using 1st derivative and 2nd derivative

Ipeak(k)=sqrt(((ikd/wo)^2)+((ikdd/(wo^2))^2))

end

figure(4)

plot(t,Ipeak,'*k',t,Im_correct,'r','LineWidth',1)

title('first and second derivative algorithm')

legend('Calc. Im using 1st derivative and 2nd derivative','Correct Im')

xlabel('Time(s)')

ylabel(' RMS Current (A)')

grid

---------------

Index exceeds array bounds.

Error in First_Second_Derivative (line 11)

ikd=(it(k+1)-it(k-1))/(2*h);

[zaid albeik]

i tryed to put for k=3:Ns -1

but another error apears

Error using plot

Vectors must be the same length.

Error in First_Second_Derivative (line 21)

plot(t,Ipeak,'*k',t,Im_correct,'r','LineWidth',1)

Answer 1

[Cris LaPierre]

We don't know what your variables it, Ns, wo, t, or Im_correct are, so we can't say for certain, but here are some thoughts.

It looks like Ns = length(it) since using Ns-1 in your for-loop counter fixed the exceeding array bounds errors. This is because you index it using k+1, so in the last loop when k=Ns, the index k+1 exceeds the size or it.

As for the new error, this error is because t does not have the same length as either Ipeak or Im_correct. You will need to check your variables to determine which it is. When plotting, each y value has to have a corresponding x value, and vice versa.