MooseUtils Namespace

DelimitedFileReader

It is often necessary to read data from files during a simulation and often this data is in a delimited format such as CSV. The DelimitedFileReader is designed for reading this data into application objects.

The DelimitedFileReader can read data organized into columns or rows. It assumes that all data, outside of the header, is numeric and can be converted to a C++ double. Additionally, it is also assumed that the first row or column defines the number of columns for the entire file, if the number of columns differs from the first row an error will be produced.

Within MOOSE this utility is utilized by the CSVReaderVectorPostprocessor, which is part of the VectorPostprocessors system. This object will be used to explain the use of the utility.

Using the DelimitedFileReader is very simple and requires three steps. First, include the utility header file with #include "DelimitedFileReader.h". Then the object is instantiated and read method is called, as shown in the unit test snippet below.

MooseUtils::DelimitedFileReader reader("data/csv/example.csv");
reader.read();

This class is required to include the filename upon construction. Optionally, a second argument providing a pointer to a libMesh Communicator object may be provided. This argument should be used when the reader is used within a MooseObject. For example, as shown in Listing 1, the CSVReaderVectorPostprocessor object passes a Communicator object to the reader. If not provided the reader will read the data on all processors. If provided it will only read on single processor and broadcast the data to the others.

It is also possible to configure how file is formatted via the various set methods, as listed below. The set methods must be called prior to the read method.

• setIgnoreEmptyLines<br> By default this all empty lines are ignored, when set to false the presence of an empty line will cause an error.

• setFormat<br> The reader is capable of reading data organized into columns or rows, this method allows for the format to be changed.

• setDelimiter<br> By default the reader will attempt to infer the delimiter from the file; however, the detection is fairly rudimentary. It inspects the file for a comma, if a comma exists then a comma is the delimiter. If it does not exist then space is the delimiter. The setDelimiter method can be used to explicitly set string to use for a delimiter.

• setHeader<br> By default the reader will attempt to detect the presence of header strings for both the row and column data formats. The setHeader method can be used to explicitly control whether header data exists. If headers exist the each data row or column will be labeled using the header and it will be accessible via the getData method by name. If no headers exist the header names are generated as "column_0", "column_1", etc. or "row_0", "row_1", etc. depending on the format settings.

• setComment<br> The string provided to this method marks content that will be ignored. Any line beginning with the character(s) will be ignored and all characters on a line that follow the character(s) will also be ignored.

  Listing 1: Construction of DelimitedFileReader object within a MooseObject initialization list.

  CSVReaderVectorPostprocessor::validParams()
  {
    InputParameters params = GeneralVectorPostprocessor::validParams();
    params.addClassDescription(
        "Converts columns of a CSV file into vectors of a VectorPostprocessor.");
    params.addRequiredParam<FileName>("csv_file",
                                      "The name of the CSV file to read. Currently, with "
                                      "the exception of the header row, only numeric "
                                      "values are supported.");
    params.addParam<bool>("header",
                          "When true it is assumed that the first row contains column headers, these "
                          "headers are used as the VectorPostprocessor vector names. If false the "
                          "file is assumed to contain only numbers and the vectors are named "
                          "automatically based on the column number (e.g., 'column_0000', "
                          "'column_0001'). If not supplied the reader attempts to auto detect the "
                          "headers.");
    params.addParam<std::string>("delimiter",
                                 "The column delimiter. Despite the name this can read files "
                                 "separated by delimiter other than a comma. If this options is "
                                 "omitted it will read comma or space separated files.");
    params.addParam<bool>(
        "ignore_empty_lines", true, "When true new empty lines in the file are ignored.");
    params.set<bool>("contains_complete_history") = true;
    params.suppressParameter<bool>("contains_complete_history");
    params.set<ExecFlagEnum>("execute_on", true) = EXEC_NONE;
    params.suppressParameter<ExecFlagEnum>("execute_on");
  
    // The value from this VPP is naturally already on every processor
    // TODO: Make this not the case!  See #11415
    params.set<bool>("_auto_broadcast") = false;
  
    return params;
  }
  
  CSVReaderVectorPostprocessor::CSVReaderVectorPostprocessor(const InputParameters & params)
    : GeneralVectorPostprocessor(params)
  {
    /// The MOOSE delimited file reader.
    MooseUtils::DelimitedFileReader csv_reader(getParam<FileName>("csv_file"), &_communicator);
  

  (framework/src/vectorpostprocessors/CSVReaderVectorPostprocessor.C)

After the data is read using the "read" method, there are two methods used for accessing the data:

• getNames: This method returns a vector of the column names as read from the header or generated based on the number of columns when a header-less file is being examined.

• getData: There are three overloaded versions of this method. One returns a reference to the

• entire data set as a vector of vectors. The others access a single vector by name or index.

Tensor Operators

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