{"id":9460,"date":"2016-02-18T09:23:27","date_gmt":"2016-02-18T01:23:27","guid":{"rendered":"http:\/\/localhost\/help\/?page_id=9460"},"modified":"2024-08-15T10:31:31","modified_gmt":"2024-08-15T02:31:31","slug":"sampling","status":"publish","type":"page","link":"https:\/\/oihelp.corporate.ifs.com\/help\/p2-server\/calculations\/sampling\/","title":{"rendered":"Sampling()"},"content":{"rendered":"\n

Format<\/h2>\n

Sampling(Expr, Method[, Interval])<\/strong><\/p>\n

Purpose<\/h2>\n

Overrides the sample method and\/or sample interval passed to tags referenced within the expression.\u00a0
\nThis function should only be used with time series data.<\/p>\n

Related: Data Transformation and Sample Methods<\/a><\/p>\n

\n

<\/i> \u00a0\u00a0New to sample methods? Download the cheat sheet!<\/a><\/p>\n<\/div>\n

Inputs<\/h2>\n

Expr<\/strong>: The expression containing the tags to be fetched.
\nBehaviour: Required
\nDimension: Collection, SingleValue, Matrix, Error, MultiCollection
\nValid data\u00a0types: Boolean, DateTime, Decimal, Integer, String, Duration, Error, Null<\/p>\n

Method<\/strong>: Fetch tags using the specified sample method. \u00a0
\nOptions: \"average\", \"linearinterpolate\", \"lastknownvalue\", \"raw\"
\nBehaviour: Required<\/p>\n

Interval<\/strong>: Fetch tags using the specified sample interval.
\nBehaviour: Optional
\nDimension: SingleValue
\nValid data\u00a0types: Decimal, Integer, Duration<\/p>\n

Notes:
\n- When intervals are expressed as numbers (decimal or integer), they are interpreted as seconds.
\n- Decimals are expressed by using a decimal point and at least 1 decimal number e.g. 60.0<\/p>\n

Examples<\/h2>\n

Expression: Sampling({tagname}, \"raw\")<\/span>
\nResult: Fetch tags using the Raw sample method<\/p>\n

Expression: Sampling({tagname}, \"average\", 60)<\/span>
\nResult:\u00a0Fetch tags using the Average sample method, with an interval of 60 seconds expressed as an integer.<\/p>\n

Expression:\u00a0Sampling({tagname}, \"lastknownvalue\", 60.0)<\/span>
\nResult:\u00a0Fetch tags using the Last Known Value sample method, with an interval of 60 seconds expressed as a decimal.<\/p>\n

Expression:\u00a0Sampling({tagname}, \"linearinterpolate\", {du'0:01'})<\/span>
\nResult:\u00a0Fetch tags using the Linear Interpolate sample method, with an interval of 1 minute expressed as a duration.<\/p>\n

The following trend shows the {Silver} tag with different sampling methods being overridden using Sampling().<\/em><\/p>\n

\"sampling-trend2\"<\/a><\/p>\n

 <\/p>\n

 <\/p>\n

Expression:\u00a0Sampling({Entity[Template]:Attribute!AttributeValue}, \"raw\")<\/span>
\nResult:\u00a0Fetch the attribute\u00a0using the Raw sample method.<\/p>\n

It is possible to retrieve very large volumes of data through indiscriminate use of the raw sample method. Retrieving large amounts of historian data across a slow network can affect system performance for all users of the system.<\/p>\n

The following trend shows an attribute being trended\u00a0using the Raw\u00a0sampling method.<\/em><\/p>\n

\"sampling-trend-2\"<\/a><\/p>\n

 <\/p>\n

Expression: Sampling({tagname}\/100, \"average\", 3600)<\/span>
\nResult:\u00a0Fetch the tag and divide it by 100, then apply the Average\u00a0sample method and a sample interval of 3600 seconds (1 hour).<\/p>\n

The following trend shows the Silver tag\u00a0being divided by 100 and then trended\u00a0using the Average\u00a0sampling method with a sample interval of 3600 seconds.<\/em><\/p>\n

\"sampling-trend-3\"<\/a><\/p>\n

Using Sampling() instead of\u00a0Tag Syntax<\/strong>:<\/p>\n

Sampling() can be used as a shortcut for expressions using tag syntax, typically used when overriding context parameters. For example:<\/p>\n

This expression:<\/p>\n

Sampling({myTag}, \"LastKnownValue\", {du'01:00'})<\/pre>\n
Is the same as:<\/p>\n
{myTag, sampleMethod=\"LastKnownValue\", sampleInterval={du'01:00'}}<\/pre>\n
Common Traps<\/h2>\n
Empty strings for the sample method are not accepted. E.g. The following example is not valid:<\/p>\n
Sampling({tagname}, \"\", 60)<\/p>\n
Expected result:\u00a0Override only the sample interval but not the sample method while fetching tags.
\nActual result: Calculation cannot be parsed as empty strings are not accepted. The equivalent correct call is:\u00a0
\nSampling({tagname}, param[sampleMethod], 60)<\/span><\/p>\n
It is possible to retrieve very large volumes of data through indiscriminate use of this function. Retrieving large amounts of historian data across a slow network can affect system performance for all users of the system.<\/p>\n
Release History<\/span><\/h2>\n