@BeginModule
@NewPage
@Name      = Arith
@Title     = Arithmetic on two datasets
@Section   = Arithmetic
@Class     = Arithmetic
@Arguments = ifile1 ifile2 ofile
@Operators = add sub mul div min max atan2

@BeginDescription
This module performs simple arithmetic of two datasets.
The number of fields in @file{ifile1} should be the same as in @file{ifile2}.
One of the input files can contain only one time step or one field.
The fields in @file{ofile} inherit the meta data from @file{ifile1} or @file{ifile2}.
@EndDescription
@EndModule


@BeginOperator_add
@Title     = Add two fields

@BeginDescription
@BeginMath
o(t,x) = i_1(t,x) + i_2(t,x)
@EndMath
@EndDescription
@EndOperator


@BeginOperator_sub

@Title     = Subtract two fields
@BeginDescription
@BeginMath
o(t,x) = i_1(t,x) - i_2(t,x)
@EndMath
@EndDescription
@EndOperator


@BeginOperator_mul
@Title     = Multiply two fields

@BeginDescription
@BeginMath
o(t,x) = i_1(t,x) * i_2(t,x)
@EndMath
@EndDescription
@EndOperator


@BeginOperator_div
@Title     = Divide two fields

@BeginDescription
@BeginMath
o(t,x) = i_1(t,x) / i_2(t,x)
@EndMath
@EndDescription
@EndOperator


@BeginOperator_min
@Title     = Minimum of two fields

@BeginDescription
@IfMan
o(t,x) = min(i_1(t,x), i_2(t,x))
@EndifMan
@IfDoc
@BeginMath
o(t,x) = \mbox{min}(i_1(t,x), i_2(t,x))
@EndMath
@EndifDoc
@EndDescription
@EndOperator


@BeginOperator_max
@Title     = Maximum of two fields

@BeginDescription
@IfMan
o(t,x) = max(i_1(t,x), i_2(t,x))
@EndifMan
@IfDoc
@BeginMath
o(t,x) = \mbox{max}(i_1(t,x), i_2(t,x))
@EndMath
@EndifDoc
@EndDescription
@EndOperator


@BeginOperator_atan2
@Title     = Arc tangent of two fields

@BeginDescription
The @math{atan2} operator calculates the arc tangent of two fields. The result is
in radians, which is between -PI and PI (inclusive).

@IfMan
o(t,x) = atan2(i_1(t,x), i_2(t,x))
@EndifMan
@IfDoc
@BeginMath
o(t,x) = \mbox{atan2}(i_1(t,x), i_2(t,x))
@EndMath
@EndifDoc
@EndDescription
@EndOperator


@BeginExample
To sum all fields of the first input file with the corresponding
fields of the second input file use:
@BeginVerbatim
   cdo add ifile1 ifile2 ofile
@EndVerbatim
@EndExample
