Remove linear trend from vectors
The Detrend block removes a linear trend from the length-M input vector, u, by subtracting the straight line that best fits the data in the least squares sense.
The least squares line, û = ax + b, is the line with parameters a and b that minimizes the quantity
for M evenly-spaced values of x, where ui is the ith element in the input vector. The output, y = u-û, is always an M-by-1 column vector.