View source for NCPLOT: Define DataSet

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[[de:NCPLOT: DataSet definieren]]

This page should help to find the right start, step and stride values.
The parameters have to be specified in a ''Dataset'' block of the [[NCPLOT]] control file.

==Preliminary remark==
The command
 <nowiki>
ncdump -h <filename>.nc
 </nowiki>
shows the header of a CF-NetCDF file in ''CDL''-syntax.
The name of the offered variables and their dimensions can be found in this metadata.

1.) Dimensions of the variables
 <nowiki>
  dimensions:
	nMesh2_node = 19508 ;
	nMesh2_edge = 37784 ;
	nMesh2_face = 18274 ;
	nMesh2_time = 1 ;
	two = 2 ;
	nMaxMesh2_face_nodes = 4 ;
	nMesh2_data_time = UNLIMITED ; // (4177 currently)
	nMesh2_layer_2d = 1 ;
	nMesh2_layer_3d = 50 ;
 </nowiki>
Hint: The dimensions are at the beginning of the file.
<br />

2.) List of variables
 <nowiki>
  float Mesh2_face_Wasserstand_2d(nMesh2_data_time, nMesh2_face) ;
	Mesh2_face_Wasserstand_2d:long_name = "Wasserstand [ face ]" ;
	Mesh2_face_Wasserstand_2d:units = "m" ;
        ...        

  float Mesh2_face_Salzgehalt_3d(nMesh2_data_time, nMesh2_layer_3d, nMesh2_face) ;
	Mesh2_face_Salzgehalt_3d:long_name = "Salzgehalt [ face ]" ;
 	Mesh2_face_Salzgehalt_2d:units = "1e-3" ;
 </nowiki>
<br />

Hint:
# The DUMP file is in CDL syntax.
# The order of the dimensions specified in Fortran is the inverted order as in the DUMP file.
# The Fortran syntax is used for the steering data.
<br />

Example: Water level
 <nowiki>
      CDL : Mesh2_face_Wasserstand_2d(nMesh2_data_time, nMesh2_face)
  Fortran : Mesh2_face_Wasserstand_2d(nMesh2_face, nMesh2_data_time)
 </nowiki>
<br />

Example: Salinity
 <nowiki>
      CDL : Mesh2_face_Salzgehalt_3d(nMesh2_data_time, nMesh2_layer_3d, nMesh2_face)
  Fortran : Mesh2_face_Salzgehalt_3d(nMesh2_face, nMesh2_layer_3d, nMesh2_data_time)
 </nowiki>
<br />

==Example: Dataset 1==
The water level should be displayed.<br />
It should begin with the 1234th result time.<br />
Overall one picture should be generated.<br />
The water level should be displayed for each result.
 <nowiki>
File           = <fileName>.nc NETCDF
Variable       = Mesh2_face_Wasserstand_2d
Start          =      1  1234
Step           =  18274     1
Stride         =      1     1
 </nowiki>
Conclusion:<br />
It is produced only one picture of the water level for the 1234-th output-date.
<br />

==Example: Dataset 2==
The water level should be displayed.<br />
It should begin with the 100th result time.<br />
The representations for 50 time points should be generated.<br />
Every sixth time point should be displayed.
 <nowiki>
File           = <fileName>.nc NETCDF
Variable       = Mesh2_face_Wasserstand_2d
Start          =      1   100
Step           =  18274    50
Stride         =      1     6
 </nowiki>
Conclusion:<br />
50 images are produced.
<br />

==Example: Dataset 3==
The 3D-salinity should be displayed.<br />
It should begin with 5th layer and the 100th result time.<br />
The representations for 9 layers and 50 time points should be generated.<br />
Every fifth layer and every 6th time point should be displayed.
 <nowiki>
File           = <fileName>.nc NETCDF
Variable       = Mesh2_face_Salzgehalt_3d
Start          =      1     5   100
Step           =  18274     9    50
Stride         =      1     5     6
 </nowiki>
Conclusion:<br />
50 x 9 = 450 images are produced.<br />
From the fifth till the 45th layer each 5th layer is displayed at each of the selected 50 time points.
<br />

==Summary==

# Use NCDUMP.
# Determine the dimensions.
# Determine the names of the variables and their dimensions.
# Invert the CDL order of dimensions.
# Determine start(:) (for location dimension = 1).
# Determine step(:)  (for location dimension = max. number of locations).
# Determine stride(:) (for location dimension = 1).
<br />

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back to [[NCPLOT.DAT]]