System Identification Toolbox

detrend

Remove trends from output-input data.

Syntax

• zd = detrend(z)
  zd = detrend(z,o,brkp)
  

Description

z is an iddata object containing the input-output data. detrend removes the trend from each signal and returns the result as an iddata object zd.

The default (o = 0) removes the zero-th order trends, i.e., the sample means are subtracted.

With o = 1, linear trends are removed, after a least-squares fit. With brkp not specified, one single line is subtracted from the entire data record. A continuous piecewise linear trend is subtracted if brkp contains breakpoints at sample numbers given in a row vector.

Note that detrend for iddata objects differs somewhat from detrend in the Signal Processing Toolbox.

Examples

Remove a V-shaped trend from the output with its peak at sample number 119, and remove the sample mean from the input.

• zd(:,1,[]) = detrend(z(:,1,[]),1,119);
  zd(:,[],1) = detrend(z(:,[],1));
  

c2d

d2c