LinearCombinationFunction

Returns the linear combination of the functions

Example input syntax

In this input file, we show how a LinearCombinationFunction may be used to combine a variety of different functions, then compare the results to a manually computed linear combination.

[Functions<<<{"href": "../../syntax/Functions/index.html"}>>>]
  [./xtimes]
    type = ParsedFunction<<<{"description": "Function created by parsing a string", "href": "MooseParsedFunction.html"}>>>
    expression<<<{"description": "The user defined function."}>>> = 1.1*x
  [../]

  [./twoxplus1]
    type = ParsedFunction<<<{"description": "Function created by parsing a string", "href": "MooseParsedFunction.html"}>>>
    expression<<<{"description": "The user defined function."}>>> = 2*x+1
  [../]

  [./xsquared]
    type = ParsedFunction<<<{"description": "Function created by parsing a string", "href": "MooseParsedFunction.html"}>>>
    expression<<<{"description": "The user defined function."}>>> = (x-2)*x
  [../]

  [./tover2]
    type = ParsedFunction<<<{"description": "Function created by parsing a string", "href": "MooseParsedFunction.html"}>>>
    expression<<<{"description": "The user defined function."}>>> = 0.5*t
  [../]

  [./the_linear_combo]
    type = LinearCombinationFunction<<<{"description": "Returns the linear combination of the functions", "href": "LinearCombinationFunction.html"}>>>
    functions<<<{"description": "This function will return Sum_over_i(w_i * functions_i)"}>>> = 'xtimes twoxplus1 xsquared tover2'
    w<<<{"description": "This function will return Sum_over_i(w_i * functions_i)"}>>> = '3 -1.2 0.4 3'
  [../]

  [./should_be_answer]
    type = ParsedFunction<<<{"description": "Function created by parsing a string", "href": "MooseParsedFunction.html"}>>>
    expression<<<{"description": "The user defined function."}>>> = 3*1.1*x-1.2*(2*x+1)+0.4*(x-2)*x+3*0.5*t
  [../]
[]

Input Parameters

functionsThis function will return Sum_over_i(w_i * functions_i)
C++ Type:std::vector<FunctionName>
Unit:(no unit assumed)
Controllable:No
Description:This function will return Sum_over_i(w_i * functions_i)
wThis function will return Sum_over_i(w_i * functions_i)
C++ Type:std::vector<double>
Unit:(no unit assumed)
Controllable:No
Description:This function will return Sum_over_i(w_i * functions_i)

Required Parameters

control_tagsAdds user-defined labels for accessing object parameters via control logic.
C++ Type:std::vector<std::string>
Controllable:No
Description:Adds user-defined labels for accessing object parameters via control logic.
enableTrueSet the enabled status of the MooseObject.
Default:True
C++ Type:bool
Controllable:No
Description:Set the enabled status of the MooseObject.

Advanced Parameters

(../moose/test/tests/functions/linear_combination_function/lcf1.i)

# LinearCombinationFunction function test
# See [Functions] block for a description of the tests

[Mesh]
  type = GeneratedMesh
  dim = 1
  xmin = 0
  xmax = 2
  nx = 10
[]

[Variables]
  [./dummy]
  [../]
[]

[Kernels]
  [./dummy_u]
    type = TimeDerivative
    variable = dummy
  [../]
[]


[AuxVariables]
  [./the_linear_combo]
  [../]
[]

[AuxKernels]
  [./the_linear_combo]
    type = FunctionAux
    variable = the_linear_combo
    function = the_linear_combo
  [../]
[]


[Functions]
  [./xtimes]
    type = ParsedFunction
    expression = 1.1*x
  [../]

  [./twoxplus1]
    type = ParsedFunction
    expression = 2*x+1
  [../]

  [./xsquared]
    type = ParsedFunction
    expression = (x-2)*x
  [../]

  [./tover2]
    type = ParsedFunction
    expression = 0.5*t
  [../]

  [./the_linear_combo]
    type = LinearCombinationFunction
    functions = 'xtimes twoxplus1 xsquared tover2'
    w = '3 -1.2 0.4 3'
  [../]

  [./should_be_answer]
    type = ParsedFunction
    expression = 3*1.1*x-1.2*(2*x+1)+0.4*(x-2)*x+3*0.5*t
  [../]
[]

[Postprocessors]
  [./should_be_zero]
    type = NodalL2Error
    function = should_be_answer
    variable = the_linear_combo
  [../]
[]

[Executioner]
  type = Transient
  dt = 0.5
  end_time = 1
[]

[Outputs]
  execute_on = 'timestep_end'
  file_base = lcf1
  hide = dummy
  exodus = false
  csv = true
[]

Example input syntax
Input Parameters