readAtTime

Read historical data from nodes of OPC UA server at specific times

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Syntax

uaData = readAtTime(uaClient,nodeList,timeVector)
uaData = readAtTime(nodeList,timeVector)

Description

uaData = readAtTime(uaClient,nodeList,timeVector) reads stored historical data from the nodes given by nodeList, at the timestamps specified in timeVector.

uaData = readAtTime(nodeList,timeVector) reads from the nodes identified by nodeList. All nodes must belong to the same connected client.

example

Examples

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Create an OPC UA client and connect the client to an OPC UA server.

uaClnt = opcua("localhost",62550);
connect(uaClnt);

Retrieve 10 minutes of historical data for the current day from the local server.

nodeId = "1:Quickstarts.HistoricalAccessServer.Data.Dynamic.Double.txt";
nodeList = opcuanode(2,nodeId,uaClnt);
timeVector = datetime('today'):minutes(10):datetime('now');
dataObj = readAtTime(uaClnt,nodeList,timeVector);

Input Arguments

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OPC UA client, specified as an OPC UA client object. The client must be connected to an OPC UA server.

List of nodes, specified as a node object or array of node objects. You can create node objects using getNamespace, browseNamespace, or opcuanode. For information on node object functions and properties, see OPC UA Node.

You can read historical data only from nodes of type Variable. If you attempt to read values from an Object node, no data is returned for that node, the status for that node is set to Bad:AttributeNotSupported, and the node is not included in the returned UaData object.

Time boundaries, specified as an array of MATLAB® datetime values returned by datetime function.

Output Arguments

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OPC UA data, returned as a vector of OPC UA data objects. Some servers interpolate or extrapolate data if it is not stored at the timestamps specified in TimeVector. If readAtTime fails to retrieve history for a given node at all the timestamps specified in TimeVector, that node is not included in the returned OPC UA data object, and a warning is issued. If all requested nodes fail, an error is generated. For more information on OPC UA data object, see OPC UA Data.

Version History

Introduced in R2015b

See Also

Functions