Approximate 1D integral of a discrete signal
SOM = integ(Y, X)
N-vector (or MxN-matrix) to be integrated (along each row).
N-vector containing the integration path of Y (default : 1:N)
value (or Mx1 vector) of the integral
integ approximates the integral of a discrete function given by the points (X(k),Y(k)) using trapezoidal approximation.