@BeginModule
@NewPage
@Name      = Selbox
@Title     = Select a box of a field
@Section   = Selection
@Class     = Selection
@Arguments = ifile ofile
@Operators = sellonlatbox selindexbox

@BeginDescription
Selects a box of the rectangular understood field.
All input fields must have the same horizontal grid.
@EndDescription
@EndModule


@BeginOperator_sellonlatbox
@Title     = Select a longitude/latitude box
@Parameter = lon1 lon2 lat1 lat2

@BeginDescription
Selects a longitude/latitude box. The user has to give the 
longitudes and latitudes of the edges of the box.
@EndDescription
@EndOperator


@BeginOperator_selindexbox
@Title     = Select an index box
@Parameter = idx1 idx2 idy1 idy2

@BeginDescription
Selects an index box. The user has to give the indexes of the 
edges of the box. The index of the left edge may be greater 
then that of the right edge.
@EndDescription
@EndOperator


@BeginParameter idx1
@Item = lon1
FLOAT    Western longitude
@Item = lon2
FLOAT    Eastern longitude
@Item = lat1
FLOAT    Southern or northern latitude
@Item = lat2
FLOAT    Northern or southern latitude
@Item = idx1
INTEGER  Index of first longitude
@Item = idx2
INTEGER  Index of last longitude
@Item = idy1
INTEGER  Index of first latitude
@Item = idy2
INTEGER  Index of last latitude
@EndParameter


@BeginExample
To select the region with the longitudes from 120E to 90W and
latitudes from 20N to 20S from all input fields use:
@BeginVerbatim
   cdo sellonlatbox,120,-90,20,-20 ifile ofile
@EndVerbatim
If the input dataset has fields on a T21 gaussian grid, the same box can
be selected with @oper{selindexbox} by:
@BeginVerbatim
   cdo selindexbox,23,48,13,20 ifile ofile
@EndVerbatim
@EndExample
