Cascade Historian™ : Version 6.4
	Dynamic Library Functions

`hist_interpolate_data`

hist_interpolate_data — interpolates a history and returns data.

Syntax

hist_interpolate_data (hist_task, history, interpolator[, start[, duration[, args ...]]])

Parameters

hist_task: The task object corresponding to the Cascade Historian. See locate_task in the Gamma manual.
history: The name of the history to use.
interpolator: The name of the interpolator to use, as described below.
start: The start of the time range of interest for query. If this value is 0 or is not supplied, it defaults to the time of the first data value available for the history.
duration: The amount of time, in seconds, over which to perform the interpolation. If this value is 0 or is not supplied, it defaults to the length of time between that specified by start and the time of the last data value available for the history.
args: Arguments to the specified interpolator, as required, passed as strings.

Returns

A binary buffer containing the requested X-Y pairs as doubles.

Description

This is a convenience function that combines hist_interpolate, hist_buffer_id_read, and hist_buffer_id_destroy. It causes the Cascade Historian to perform the requested interpolation on its history data, producing a temporary buffer which is read (copied to the user Gamma program) and subsequently destroyed.

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 Cogent C API function HI_InterpolateData.

Example

Gamma> length (a = hist_buffer2array (hist_interpolate_data(tsk, "p6", "PeriodicInterpolator", 0.0, 0.0, "0.1")));
37
Gamma> a[12];
{HI_stVALUE (value . 103.018446) (xaxis . 1025721206.7)}


hist_interpolate		hist_latest