How can I find out the solution of second derivative pick detection. I have already done 1st derivative pick detection now I want use the same method for 2nd derivatives..

My first derivative Pick detection code is given bellow:

clear;

clc;

t=-5:1/20:5;

ind1=zeros(1,length(t));

x=sin(2*pi*t)+cos(3*pi*t);

% x=sin(2*pi*t);

g=diff(x);

ind = find(g(1:end-1).*g(2:end) < 0)+1;

plot(t,x, t(ind), x(ind), 'o');

Now, I want to write second derivative pick direction by using above code.

The second derivative equation is

Y1(n) = [x(n)-2x(n-2)+x(n-4)]

Please, help me to write the code for Second derivative