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By the end of this chapter you will be able to:

  • Use a loop pipe to read a Stream's own historic data when generating a new Stream Set
  • Use Data to Read = Previous

Files containing details of metered usage can be found in the input files, in the directory:
…\inputData\MeteredUsage\input
Read in a copy of these files on the CenterView server:

  • Add a sequence:
    • Find the button - Show the list of Sequences in the left-hand menu bar
    • Press to create a new sequence
    • Enter the following details into the sequence configuration form:
    • Name: MeteredSeq
    • Start Value: 1
    • Press OK to save your changes
  • Create a new model view
  • Create a file collector to read files of metered usage data:
  • Add a File Collector to your model, with Name Metered Usage
  • Enter the following settings:
    • Input Directory Expr.: "MeteredUsage/input"
    • File Pattern Expression: ".*"
    • Enabled: ticked
    • Number of Header Lines: 1
    • Allow Non-Scheduled Collection: ticked
  • Create the columns in the file collector and create a stream
  • Update the File Pattern Expression in the file collector to: "meteredUsage" + nextValue("MeteredSeq") + ".txt" (the file names have a sequence number)
  • Add a merge called Total Metered Usage
  • Complete configuration of Total Metered Usage:
  • Add a pipe from Metered Usage into Total Metered Usage, with Name in
  • Add the grouping key CustomerRef to the pipe in
  • Drag all Attributes from Metered Usage into Total Metered Usage
  • Add a pipe from the Stream into itself
  • Edit details for the loop pipe:
    • Set the Name to prev
    • Set Data to Read to Previous
    • Add the grouping key CustomerRef
  • In the stream Total Metered Usage:
    • Set the expression on the Attribute CustomerRef to _key[1]
    • Set the expression on the Attribute MeteredUsage to: prev.MeteredUsage + in.MeteredUsage

This expression will add the value from the previous Stream Set – that is, the data from the previous run - for the current key value to the new value being read in for this key value
In this way you will build a running total for metered usage for each customer

  • Save your changes

    You cannot, in most cases, do a Merge or Aggregate directly from a File Collector. This is because when bringing data in for a Merge or Aggregate CenterView needs to sort the data (by the grouping keys being used). When reading data in from a file, there is no way for CenterView to guarantee the order of the records. When you want to Merge or Aggregate data from files, load this first into a Calculate Stream and then add a Merge/Aggregate Stream.

  • Run Analysis on Total Metered Usage three times
  • You will see in Metered Usage that in each Stream Set a file has been read in
  • Look at the Stream Sets generated in Total Metered Usage - you will see that a running total is maintained for each customer as each new data set is read in
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