PiecewiseLinear

Linearly interpolates between pairs of x-y data

Description

The PiecewiseLinear function performs linear interpolations between user-provided pairs of x-y data. The x-y data can be provided in three ways. The first way is through a combination of the x and y parameters, which are lists of the x and y coordinates of the data points that make up the function. The second way is in the xy_data parameter, which is a list of pairs of x-y data that make up the points of the function. This allows for the function data to be specified in columns by inserting line breaks after each x-y data point. Finally, the x-y data can be provided in an external file containing comma-separated values. The file name is provided in data_file, and the data can be provided in either rows (default) or columns, as specified in the format parameter.

By default, the x-data corresponds to time, but this can be changed to correspond to x, y, or z coordinate with the axis line. If the function is queried outside of its range of x data, it returns the y value associated with the closest x data point, unless the parameter extrap is set to true, in which case extrapolation is performed instead.

Example Input Syntax

[Functions]
  [./ic_function]
    type = PiecewiseLinear
    data_file = piecewise_linear_columns.csv #Will generate error because data is expected in rows
    scale_factor = 1.0
  [../]
[]

Input Parameters

axisThe axis used (x, y, or z) if this is to be a function of position
C++ Type:MooseEnum
Unit:(no unit assumed)
Options:x, y, z
Controllable:No
Description:The axis used (x, y, or z) if this is to be a function of position
extrapFalseIf true, extrapolates when sample point is outside of abscissa range
Default:False
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:If true, extrapolates when sample point is outside of abscissa range
scale_factor1Scale factor to be applied to the ordinate values
Default:1
C++ Type:double
Unit:(no unit assumed)
Controllable:Yes
Description:Scale factor to be applied to the ordinate values

Optional Parameters

control_tagsAdds user-defined labels for accessing object parameters via control logic.
C++ Type:std::vector<std::string>
Unit:(no unit assumed)
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
Unit:(no unit assumed)
Controllable:No
Description:Set the enabled status of the MooseObject.

Advanced Parameters

data_fileFile holding CSV data
C++ Type:FileName
Unit:(no unit assumed)
Controllable:No
Description:File holding CSV data
formatrowsFormat of csv data file that is in either in columns or rows
Default:rows
C++ Type:MooseEnum
Unit:(no unit assumed)
Options:columns, rows
Controllable:No
Description:Format of csv data file that is in either in columns or rows
x_index_in_file0The abscissa index in the data file
Default:0
C++ Type:unsigned int
Unit:(no unit assumed)
Controllable:No
Description:The abscissa index in the data file
x_titleThe title of the column/row containing the x data in the data file
C++ Type:std::string
Unit:(no unit assumed)
Controllable:No
Description:The title of the column/row containing the x data in the data file
xy_in_file_onlyTrueIf the data file only contains abscissa and ordinate data
Default:True
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:If the data file only contains abscissa and ordinate data
y_index_in_file1The ordinate index in the data file
Default:1
C++ Type:unsigned int
Unit:(no unit assumed)
Controllable:No
Description:The ordinate index in the data file
y_titleThe title of the column/row containing the y data in the data file
C++ Type:std::string
Unit:(no unit assumed)
Controllable:No
Description:The title of the column/row containing the y data in the data file

Data From Csv File Parameters

json_uoJSONFileReader holding the data
C++ Type:UserObjectName
Unit:(no unit assumed)
Controllable:No
Description:JSONFileReader holding the data
x_keysOrdered vector of keys in the JSON tree to obtain the abscissa
C++ Type:std::vector<std::string>
Unit:(no unit assumed)
Controllable:No
Description:Ordered vector of keys in the JSON tree to obtain the abscissa
y_keysOrdered vector of keys in the JSON tree to obtain the ordinate
C++ Type:std::vector<std::string>
Unit:(no unit assumed)
Controllable:No
Description:Ordered vector of keys in the JSON tree to obtain the ordinate

Data From Json Parameters

xThe abscissa values
C++ Type:std::vector<double>
Unit:(no unit assumed)
Controllable:No
Description:The abscissa values
xy_dataAll function data, supplied in abscissa, ordinate pairs
C++ Type:std::vector<double>
Unit:(no unit assumed)
Controllable:No
Description:All function data, supplied in abscissa, ordinate pairs
yThe ordinate values
C++ Type:std::vector<double>
Unit:(no unit assumed)
Controllable:No
Description:The ordinate values

Data From Input File Parameters

(moose/test/tests/misc/check_error/function_file_test1.i)

# Test for usage of missing function
[Mesh]
  [./square]
    type = GeneratedMeshGenerator
    nx = 2
    ny = 2
    dim = 2
  [../]
[]

[Variables]
  active = 'u'

  [./u]
    order = FIRST
    family = LAGRANGE
    [./InitialCondition]
      type = FunctionIC
      function = ic_function
    [../]
  [../]

[]

[Functions]
  [./ic_function]
    type = PiecewiseLinear
    data_file = piecewise_linear_columns.csv #Will generate error because data is expected in rows
    scale_factor = 1.0
  [../]
[]

[Kernels]
  active = 'diff'

  [./diff]
    type = Diffusion
    variable = u
  [../]
[]

[BCs]
  active = 'left right'

  [./left]
    type = DirichletBC
    variable = u
    boundary = 3
    value = 0
  [../]

  [./right]
    type = DirichletBC
    variable = u
    boundary = 1
    value = 1
  [../]
[]

[Executioner]
  type = Steady

  solve_type = 'PJFNK'
[]

[Outputs]
  file_base = out
[]

Description
Example Input Syntax
Input Parameters