Selectively apply a set of scale and offset values to data readings.

A JSON document configures the set of scale factors and offset values to add to readings. Each scale and offset value is associated with a regular expression whcih is matches against the asset name of the reading in the asset. Optionally a datapoint regular expression may also be given, this is used to match the datapoint within a matching asset.

Caution, if multiple regular expressions match a single asset and datapoint then all of the scale and offset values will be applied to the asset/datapoint.

The filter supports the following configuration items:

enable

A switch to control if the filter should take effect or not

factors

A JSON document which contains an array of scale factors to apply. Each element in the arary is a JSON object with the following properties:

asset

A regular expression that should match the asset name

datapoint

A regular expression that should match the data point within the asset

scale

The scale factor to apply to the matching asset and data point

offset

An offset value to apply to the matching asset and data point

{ "factors" : [
     {
       "asset"     : "environment",
       "datapoint" : "temperature",
       "scale"     : 1.8,
       "offset"    : 32
     },
     {
       "asset"     : "environment",
       "datapoint" : "humidity",
       "scale"     : 0.1,
       "offset"    : 0
     }
  ]
}

To build FogLAMP "scale-set" C++ filter plugin:

$ mkdir build
$ cd build
$ cmake ..
$ make

• By default the FogLAMP develop package header files and libraries are expected to be located in /usr/include/foglamp and /usr/lib/foglamp
• If FOGLAMP_ROOT env var is set and no -D options are set, the header files and libraries paths are pulled from the ones under the FOGLAMP_ROOT directory. Please note that you must first run 'make' in the FOGLAMP_ROOT directory.

You may also pass one or more of the following options to cmake to override this default behaviour:

• FOGLAMP_SRC sets the path of a FogLAMP source tree
• FOGLAMP_INCLUDE sets the path to FogLAMP header files
• FOGLAMP_LIB sets the path to FogLAMP libraries
• FOGLAMP_INSTALL sets the installation path of Random plugin

NOTE:

• The FOGLAMP_INCLUDE option should point to a location where all the FogLAMP header files have been installed in a single directory.
• The FOGLAMP_LIB option should point to a location where all the FogLAMP libraries have been installed in a single directory.
• 'make install' target is defined only when FOGLAMP_INSTALL is set

Examples:

• no options

  $ cmake ..

• no options and FOGLAMP_ROOT set

  $ export FOGLAMP_ROOT=/some_foglamp_setup

  $ cmake ..

• set FOGLAMP_SRC

  $ cmake -DFOGLAMP_SRC=/home/source/develop/FogLAMP ..

• set FOGLAMP_INCLUDE

  $ cmake -DFOGLAMP_INCLUDE=/dev-package/include ..

• set FOGLAMP_LIB

  $ cmake -DFOGLAMP_LIB=/home/dev/package/lib ..

• set FOGLAMP_INSTALL

  $ cmake -DFOGLAMP_INSTALL=/home/source/develop/FogLAMP ..

  $ cmake -DFOGLAMP_INSTALL=/usr/local/foglamp ..