@BeginModule
@Name      = Subtrend
@Title     = Subtract a trend
@Section   = Regression
@Class     = Regression
@Arguments = ifile1 ifile2 ifile3 ofile
@Operators = subtrend
@EndModule


@BeginOperator_subtrend
@Title     = Subtract trend

@BeginDescription
This operator is for subtracting a trend computed by the operator @mod{trend}.
@IfMan
It is

o(t,x) = i_1(t,x) - (i_2(1,x) + i_3(1,x)*t)
@EndifMan
@IfDoc
It is
@BeginDisplayMath
o(t,x) = i_1(t,x) - (i_2(1,x) + i_3(1,x) \cdot t)
@EndDisplayMath
@EndifDoc
where t is the time steps.
@EndDescription
@EndOperator


@BeginExample
The typical call for detrending the data in @file{ifile} and storing the detrended data in @file{ofile} is:
@BeginVerbatim
  cdo trend ifile afile bfile
  cdo subtrend ifile afile bfile ofile
@EndVerbatim
The result is identical to a call of the operator @mod{detrend}:
@BeginVerbatim
  cdo detrend ifile ofile
@EndVerbatim
@EndExample
