detrend

Signal Processing Toolbox

Remove linear trends.

y = detrend(x)
y = detrend(x,0)

Description

detrend removes the mean value or linear trend from a vector or matrix, usually for FFT processing.

y = detrend(x)

removes the best straight-line fit from vector x and returns it in y. If x is an array, detrend removes the trend from each column.

y = detrend(x,0)

removes the mean value from vector x or, if x is an array, from each column of the array.

Algorithm

detrend computes the least-squares fit of a straight line to the data and subtracts the resulting function from the data. The main part of the algorithm is

m = length(x);
a = [(1:m)'/m ones(m,1)];
y = x - a*(a\x);

To obtain the equation of the straight-line fit, use polyfit.