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The SEDRIS Data Representation Model
APPENDIX A - Classes Irregular Axis |
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An instance of this DRM class is an <Axis> instance that does not use a constant spacing between tick marks.
Data taken at times 1, 2, 5, 10, 50, and 100 seconds after some start time are collected on an <Irregular Axis> instance.
Radiosonde data, including temperature, humidity, wind speed, and wind direction, is generally reported as a function of pressure height. Data are reported only when there is a significant change in one of the dependent variables. Accordingly, the pressure heights are captured at unpredictable, irregular intervals. They are best collected in an <Irregular Axis> instance.
It depends how many values are missing. If only one or two values are missing from a long regular sequence, it may be preferable to use a <Regular Axis> instance and indicate the missing data points with an appropriate <Property Characteristic> instance.
If the data were truly irregular, which is to say that there is only one point at each x-value and only one point at each y-value, do not use irregular x- and y-axes. Instead, use a single regular axis to give each point an index and make the x- and y-values dependent variables.
On the other hand, if the points are not quite that irregular, but rather data were taken at each (or most) combination of x- and y-values, irregular axes may be appropriate. This would mean that the data really did form a grid.
The axis_type field specifies the property being described by the <Axis> instance.
The axis_value_count specifies the number of tick marks along the <Axis> instance.
The axis_value_array field specifies the tick mark values, which shall be arranged in monotonically ascending or monotonically descending order.
The value_unit field specifies the unit of measurement of the <Irregular Axis> instance, which shall be compatible with the requirements imposed by its axis_type value.
If the specified axis_type does not require a unit of measurement, value_unit shall be set to EUC_UNITLESS.
The value_scale field specifies the scale applicable to value_unit.
If the specified axis_type does not require a scale, value_scale shall be set to ESC_UNI.
The value of the interpolation_type field allows the data provider to indicate how best to interpolate the data to points that are between grid points on the axis represented by the <Irregular Axis> instance.
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