Retrieval page - Data sampling options (XY Plot)
Data sampling determines the method used to select and analyze a subset of data. The following data sampling options are available.
Sampling Type | Description |
|---|---|
Average | Adds the values of all good raw data within each defined sampling interval, and divides the sum by the number of good values. If one or more non-good raw values are also found within a sampling interval, the quality of the average aggregate for that sampling interval is returned as uncertain. |
Cumulative Total | Returns the cumulative total of all good raw values within each defined sampling interval. This is useful when used with a counter, because when the counter resets to zero, the cumulative total will continue counting up from the point of the reset. If one or more non-good raw values are also found within a sampling interval, the quality of the cumulative total aggregate for that sampling interval is returned as Uncertain . |
Delta | Returns the difference between the first and last good raw values within each defined sampling interval. Note the following:
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End | Retrieves the last raw value within each defined sampling interval, and returns it with the timestamp at which that value occurs. The time stamp is the time stamp of the end of the interval. If the value is non-good, the quality of the aggregate for that sampling interval is returned as Uncertain . |
Interpolative | Returns an interpolated value for each defined sampling interval boundary. The type of interpolation performed depends on the data provider, but will be either sample and hold or linear interpolation. The default interpolation type for the Incuity server is SampleAndHold , which returns the last raw value prior to each defined Sampling Interval boundary . |
Linear | Returns the good raw value (if available) at each defined sampling interval boundary. If no good raw value is available at the boundary, returns the calculated linear straight-line interpolation between the nearest good raw values preceding and following the boundary. The formula used in this case is: BoundaryVALUE = (((BoundaryTIME - PreceedingTIME) / (FollowingTIME - PreceedingTIME)) X (FollowingVALUE - PreceedingVALUE)) + PreceedingVALUE . |
Maximum | Returns the maximum good raw value within each defined sampling interval, and returns that value with the timestamp of the start of the interval. If the same maximum value exists at more than one timestamp, the oldest one is retrieved. If a non-good raw value within a sampling interval is higher than the good maximum value, the quality of the aggregate for that sampling interval is returned as Uncertain . |
Maximum Actual Time | Returns the maximum good raw value within each defined sampling interval, and returns that value with the timestamp at which the value occurs. If the same maximum value exists at more than one timestamp, the oldest one is returned. If a non-good raw value within a sampling interval is higher than the good maximum value, the quality of the aggregate for that sampling interval is returned as Uncertain . |
Maximum Sample and Hold | Returns the maximum good raw value within each defined sampling interval, and returns that value with the timestamp of the start of the interval. If the same maximum exists at more than one timestamp, the oldest one is returned. If a non-good raw value within a sampling interval is greater than the good maximum value, the quality of the aggregate for that sampling interval is returned as Uncertain .This sampling type uses Sample and Hold interpolation to determine the beginning held value at the start of each interval. This held value is the last good raw value occurring on or before the starting time of that interval. This beginning held value is also considered to be within the interval, and is therefore taken into consideration as a possible maximum. It will be the maximum value if no other values are present in the interval. |
Minimum | Returns the minimum good raw value within each defined sampling interval, and returns that value with the timestamp of the start of the interval. If the same minimum value exists at more than one timestamp, the oldest one is returned. If a non-good raw value within a sampling interval is lower than the good minimum value, the quality of the aggregate for that sampling interval is returned as Uncertain . |
Minimum Actual Time | Returns the minimum good raw value within each defined sampling interval, and returns that value with the timestamp at which the value occurs. If the same minimum exists at more than one timestamp, the oldest one is returned. If a non-good raw value within a sampling interval is lower than the good minimum value, the quality of the aggregate for that sampling interval is returned as Uncertain . |
Minimum Sample and Hold | Returns the minimum good raw value within each defined sampling interval, and returns that value with the timestamp of the start of the interval. If the same minimum value exists at more than one timestamp, the oldest one is returned. If a non-good raw value within a sampling interval is less than the good minimum value, the quality of the aggregate for that sampling interval is returned as Uncertain .This sampling type uses Sample and Hold interpolation to determine the beginning held value at the start of each interval. This held value is the last good raw value occurring on or before the starting time of that interval. This beginning held value is also considered to be within the interval, and can be a possible minimum value. It will be the minimum value if no other values are present in the interval. |
Range | Returns the difference between the raw maximum and raw minimum values within each defined sampling interval. If only one value exists in the interval, the range is zero. Note that the range is always zero or positive. If any non-good values exist in the interval, they are ignored, and the quality of the aggregate for that interval is returned as Uncertain . |
Sample and hold | Returns the last raw value prior to each defined sampling interval boundary and keeps it until it changes. The quality of the returned value will match that of the raw value. Because the last raw values are held across intervals, the same raw value may potentially be returned for more than one interval boundary. |
Standard Deviation | Returns the standard deviation of good raw values within each defined sampling interval, calculated using the formula SQRT( SUM ( ((X - Avg(X))**2 ) / (n - 1)) where X is each good raw value in the interval, Avg(X) is the average of the good raw values, and n is the number of good raw values in the interval. For intervals where n=1 , a value of zero is returned. |
Start | Returns the first raw value within each defined sampling interval, and returns it with the timestamp at which that value occurs. The timestamp is the timestamp of the beginning of the interval. If the value is non-good, the quality of the aggregate for that sampling interval is returned as Uncertain . |
Sum | Returns the sum of all good raw values within each defined sampling interval. If one or more non-good raw values are also found within a sampling interval, the quality of the sum aggregate for that sampling interval is returned as Uncertain . |
Time Average | Returns the time weighted average data over the resample interval. This sampling type uses Linear sampling to return a boundary value for each defined sampling interval boundary. A straight line is then drawn between the starting and ending boundary values of each interval, and the area under the line calculated (1/2 base X height) + (base X height)) . The area under the line is the divided by the length of the interval to yield the time-weighted average for each bounded interval. |
Time Average Sample and Hold | Uses Sample and Hold interpolation to return a boundary value for each defined sampling interval boundary. This differs from the Time Average sampling type, which uses Linear interpolation to determine the boundary values, and also differs from Time Average in the assumption made as for the value between raw data values. For Time Average, the value between each good raw value is assumed to change continuously (in a straight line) from the first value to the second. For Time Average Sample and Hold, the value is assumed to hold at the first value for the entire length of time prior to receipt of the second value. The rectangular area between each value is calculated using the formula ((end time – start time) * start value) . Each of these areas is then added to the total interval area. The total interval area is divided by the total time of the interval to yield the time-weighted average for that interval. |
Total | Returns the total value (time integral) of the data over the resample interval. This sampling type uses time average sampling to return a time-weighted average for each defined sampling interval. The time-weighted average is multiplied by the length of the interval, in seconds, to give the total value normalized to seconds. |
Total Sample and Hold | Uses Time Average Sample and Hold sampling to return a time-weighted average for each defined sampling interval. The time-weighted average is multiplied by the length of the interval, in seconds, to give the Total Sample and Hold value normalized to seconds. |
Variance | Returns the variance over the sample interval. This sampling type uses Standard Deviation sampling to return the standard deviation for each defined sampling interval. The standard deviation is squared to give the variance for the interval. |
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