@BeginModule
@NewPage
@Name      = Ydayarith
@Title     = Multi-year daily arithmetic
@Section   = Arithmetic
@Class     = Arithmetic
@Arguments = ifile1 ifile2 ofile
@Operators = ydayadd ydaysub ydaymul ydaydiv

@BeginDescription
This module performs simple arithmetic of a time series and one
timestep with the same day of year. For each field in @file{ifile1}
the corresponding field of the timestep in @file{ifile2} with the
same day of year is used. The header information in @file{ifile1}
have to be the same as in @file{ifile2}. Usually @file{ifile2} is generated
by an operator of the module @mod{YDAYSTAT}.
@EndDescription
@EndModule


@BeginOperator_ydayadd
@Title     = Add multi-year daily time series

@BeginDescription
Adds a time series and a multi-year daily time series.
@EndDescription
@EndOperator


@BeginOperator_ydaysub
@Title     = Subtract multi-year daily time series

@BeginDescription
Subtracts a time series and a multi-year daily time series.
@EndDescription
@EndOperator


@BeginOperator_ydaymul
@Title     = Multiply multi-year daily time series

@BeginDescription
Multiplies a time series and a multi-year daily time series.
@EndDescription
@EndOperator


@BeginOperator_ydaydiv
@Title     = Divide multi-year daily time series

@BeginDescription
Divides a time series and a multi-year daily time series.
@EndDescription
@EndOperator


@BeginExample
To subtract a multi-year daily time average from a time series use:
@BeginVerbatim
   cdo ydaysub ifile -ydayavg ifile ofile
@EndVerbatim
@EndExample
