The VectorField class supplies two-dimensional vector field data.
Header file: ncarg/hlu/VectorField.h Class name: vectorFieldClass Class pointer: NhlvectorFieldClass Fortran class pointer: NHLFVECTORFIELDCLASS Superclass: DataItem Composite classes: <None>
+---------------------------------------------------------------+ | VectorField Resource Set | |---------------------------------------------------------------| | NAME TYPE ACCESS | | CLASS DEFAULT | |===============================================================| | vfDataArray NhlTGenArray RCSG | | VfDataArray NULL | |---------------------------------------------------------------| | vfUDataArray NhlTGenArray RCSG | | VfUDataArray NULL | |---------------------------------------------------------------| | vfVDataArray NhlTGenArray RCSG | | VfVDataArray NULL | |---------------------------------------------------------------| | vfXArray NhlTGenArray RCSG | | VfXArray NULL | |---------------------------------------------------------------| | vfYArray NhlTGenArray RCSG | | VfYArray NULL | |---------------------------------------------------------------| | vfPolarData NhlTBoolean RCSG | | VfPolarData False | |---------------------------------------------------------------| | vfCopyData NhlTBoolean RCSG | | diCopyData True | |---------------------------------------------------------------| | vfExchangeDimensions NhlTBoolean RCSG | | VfExchangeDimensions False | |---------------------------------------------------------------| | vfExchangeUVData NhlTBoolean RCSG | | VfExchangeUVData False | |---------------------------------------------------------------| | vfSingleMissingValue NhlTBoolean RCSG | | VfSingleMissingValue True | |---------------------------------------------------------------| | vfMissingUValueV NhlTVariable RCSG | | VfMissingUValueV NULL | |---------------------------------------------------------------| | vfMissingVValueV NhlTVariable RCSG | | VfMissingVValueV NULL | |---------------------------------------------------------------| | vfMagMinV NhlTVariable RCSG | | VfMagMinV <Dynamic> | |---------------------------------------------------------------| | vfMagMaxV NhlTVariable RCSG | | VfMagMaxV <Dynamic> | |---------------------------------------------------------------| | vfUMinV NhlTVariable RCSG | | VfUMinV <Dynamic> | |---------------------------------------------------------------| | vfUMaxV NhlTVariable RCSG | | VfUMaxV <Dynamic> | |---------------------------------------------------------------| | vfVMinV NhlTVariable RCSG | | VfVMinV <Dynamic> | |---------------------------------------------------------------| | vfVMaxV NhlTVariable RCSG | | VfVMaxV <Dynamic> | |---------------------------------------------------------------| | vfXCStartV NhlTVariable RCSG | | VfXCStartV <Dynamic> | |---------------------------------------------------------------| | vfXCEndV NhlTVariable RCSG | | VfXCEndV <Dynamic> | |---------------------------------------------------------------| | vfYCStartV NhlTVariable RCSG | | VfYCStartV <Dynamic> | |---------------------------------------------------------------| | vfYCEndV NhlTVariable RCSG | | VfYCEndV <Dynamic> | |---------------------------------------------------------------| | vfXCStartSubsetV NhlTVariable RCSG | | VfXCStartSubsetV <Dynamic> | |---------------------------------------------------------------| | vfXCEndSubsetV NhlTVariable RCSG | | VfXCEndSubsetV <Dynamic> | |---------------------------------------------------------------| | vfYCStartSubsetV NhlTVariable RCSG | | VfYCStartSubsetV <Dynamic> | |---------------------------------------------------------------| | vfYCEndSubsetV NhlTVariable RCSG | | VfYCEndSubsetV <Dynamic> | |---------------------------------------------------------------| | vfXCStartIndex NhlTInteger RCSG | | VfXCStartIndex <Dynamic> | |---------------------------------------------------------------| | vfXCEndIndex NhlTInteger RCSG | | VfXCEndIndex <Dynamic> | |---------------------------------------------------------------| | vfYCStartIndex NhlTInteger RCSG | | VfYCStartIndex <Dynamic> | |---------------------------------------------------------------| | vfYCEndIndex NhlTInteger RCSG | | VfYCEndIndex <Dynamic> | |---------------------------------------------------------------| | vfXCActualStartF NhlTFloat RCSG | | VfXCActualStartF <Dynamic> | |---------------------------------------------------------------| | vfXCActualEndF NhlTFloat RCSG | | VfXCActualEndF <Dynamic> | |---------------------------------------------------------------| | vfYCActualStartF NhlTFloat RCSG | | VfYCActualStartF <Dynamic> | |---------------------------------------------------------------| | vfYCActualEndF NhlTFloat RCSG | | VfYCActualEndF <Dynamic> | |---------------------------------------------------------------| | vfXCStride NhlTInteger RCSG | | VfXCStride 1 | |---------------------------------------------------------------| | vfYCStride NhlTInteger RCSG | | VfYCStride 1 | +---------------------------------------------------------------+
VectorField handles both regularly and irregularly spaced rectangular data arrays. It assumes the grid is regularly spaced unless you set one or both of the supplementary array resources, vfXArray and vfYArray, that specify the possibly irregularly spaced location of data points along their respective data coordinate axes.
The VectorField object automatically converts data specified using a variety of numerical types into the NhlTFloat type expected by the receiving plot object. The types it currently handles are as follows:
VectorField can pre-process the data arrays in a number of ways before handing them off to the receiving object. You can exchange the array dimensions or the U and V components of the data. You can reverse the direction of the data along either or both axes with suitable specification of the endpoints in data coordinate space. You can also make an overly dense array of data more sparse by specifying an index stride value along either or both the X and the Y dimensions.
Instead of sending the complete arrays to the receiver object, you can pass it any contiguous rectangular subset of the arrays, specified either by array index or by location in the data coordinate space. Unless the data dimension sizes also change, VectorField preserves the subset resource settings when the data change. This makes it easy to step through a subset of a time or level related series of data. If the dimension sizes change, VectorField assumes that the meaning of the data has also changed and that therefore the currently defined subset, besides potentially being out of range, is most likely not meaningful. In this case, the subset resources are reset to include all elements of the data arrays.
1.
Note that even if the values of the coordinate array resources
(vfXArray and vfYArray) are actually equally spaced,
plot objects such as ContourPlot currently use the
presence of a coordinate array as a signal that the data are
irregularly spaced along the axis in question. In this case the
plot object uses an IrregularTransformation object rather
than a LogLinTransformation object when plotting the
data. The practical consequence, besides a small performance penalty,
is that it will then be necessary to overlay the plot on a
LogLinPlot if it is desired to make the X Axis
logarithmic. If the axis is actually regularly spaced, you can avoid this
problem by setting vf...Array to NULL,
vf...CStartV to the value of the array's first element, and
vf...CEndV to the value of the array's last element.
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