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:
![[Note]](images/note.gif) | 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)}
