| Cogent C API and Utilities : Version 6.4 | ||
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 | Cascade Historian Functions |  |
| Cogent C API and Utilities : Version 6.4 | ||
|---|---|---|
| | Cascade Historian Functions | |
#include <cogent.h>
ST_STATUS HI_InterpolateData(IP_hTASK historian, char* histname, char* interpolator, double start, double duration, int nxargs, char** xargs, HI_stVALUE** values, int* nvalues );
The task pointer to the Cascade Historian program.
The name of a history.
The name of the interpolator to use, as described below.
The start of the time range of interest for query. If this value is 0, it defaults to the time of the first data value available for the history.
The amount of time, in seconds, over which to perform the interpolation. If this value is 0, it defaults to the length of time between that specified by start and the time of the last data value available for the history.
The number of extra arguments to the interpolator.
The array of extra arguments to the interpolator, as strings.
A pointer to an HI_stVALUE*. This is a return argument.
The number of elements in values. This is a return argument.
ST_OK on success. Otherwise ST_ERROR, and the retbuf will contain a NULL-terminated character string with an error message. If the return value is ST_OK, the retbuf may not contain useful information.
This is a convenience function that combines HI_Interpolate, HI_BufferIDLength, HI_BufferIDRead, and HI_BufferIDDestroy. It causes the Cascade Historian to perform an interpolation on its history data, producing a new, temporary, un-named history, which is then copied to the client program. The resulting data is returned in values, and is nvalues in length.
![[Note]](images/note.gif) | The code for this function can be viewed in the Example for HI_Interpolate. |
You are responsible for freeing the values, using the function ME_Free. The xargs array is an array of NULL-terminated strings. Numeric arguments are passed as strings containing their printable ASCII representations.
The following choices are available for the interpolator argument:
| The NoInterpolator function is currently the only one that requires no additional parameters, making it possible to not supply start or duration. For the other interpolator functions, setting start or duration to 0 forces the default values. |
NoInterpolator simply returns all data that falls within the specified time range. No other processing is performed. When calling the HI_Interpolate function, this interpolator requires no extra arguments (nxargs = 0, xargs = NULL).
PeriodicInterpolator generates data as Y vs. time on an even time interval. The first extra argument is a double-precision float indicating the time interval in seconds. The second (optional) extra argument is a double-precision float indicating the maximum gap time: if provided and the time between two data samples exceeds this threshold, then data cannot be interpolated between the points. This suppresses generating interpolated data during 'gaps' in the data.
RelativeInterpolator generates Y vs. X at all known values of X. The first extra argument is a string indicating the history name for X. The history argument provided to interpolate command (or the histname argument provided to HI_Interpolate function) is used as the Y history.
FixedRelativeInterpolator generates Y vs. X on an even time interval. The first extra argument is a string indicating the history name for X. The second extra argument is a double specifying the time interval. The history argument provided to interpolate command (or the histname argument provided to HI_Interpolate function) is used as the Y history.
This function corresponds to the Cascade Historian hist_interpolate_data dynamic library function.
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| HI_Interpolate |  | HI_Latest |
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