DETREND removes the trend from data, NaN's are considered as missing values

DETREND is fully compatible to previous Matlab and Octave DETREND with the following features added:
- handles NaN's by assuming that these are missing values
- handles unequally spaced data
- second output parameter gives the trend of the data
- compatible to Matlab and Octave

[...]=detrend([t,] X [,p])
removes trend for unequally spaced data
t represents the time points
X(i) is the value at time t(i)
p must be a scalar

[...]=detrend(X,0)
[...]=detrend(X,'constant')
removes the mean

[...]=detrend(X,p)
removes polynomial of order p (default p=1)

[...]=detrend(X,1) - default
[...]=detrend(X,'linear')
removes linear trend

[X,T]=detrend(...)

X is the detrended data
T is the removed trend

see also: SUMSKIPNAN, ZSCORE