Some specialized Natgrid control parameters


This module discusses the control parameters for:
Negative values
Vertical orientation
Duplicate input coordinates

Negative values

The control parameter non determines whether negative values are allowed as interpolated values. The default is to allow them. If disallowed, by setting the value of the control parameter non to 1, then any value that would otherwise be negative is set to zero. The plots in Example 5 illustrate this. Compare the plot that allows negative values with the plot that does not allow them.

This feature is useful if you have a function, such a pressure, that should never have a negative value.

Vertical orientation

The control parameter upd determines the ordering of the second dimension of the output array. The default, "upd = 1", implies a south to north ordering; setting upd to 0 reverses the order.

Duplicate input coordinates

Natgrid automatically culls duplicate input coordinates. However, if two input points have the same X/Y coordinates but different data values, then a fatal error is issued. Natgrid reports an informational message about the input coordinates that have been culled, up to a maximum number of such messages. The control parameter mdm specifies the maximum number of messages issued about duplicate points; the default is 10. If mdm is set to zero, then the culling of duplicate points will proceed silently.
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