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dsc

• name:
  dsc
• synopsis: dsc [-rpn_expression=" first-rpn-expression"] [-rpn_file=" filename"] -variable= variable_name,filename [-command=" rpn-expression"] -result= variable_name,filename," rpn-expression" [-test=" rpn-expression"] [-independent_variable=" name"] [-format=" format-string"]
• description:
  

  The Data Set Calculator is one of the most powerful programs in the Toolkit, being something like a command-line spreadsheet. It allows use of an arbitrary number of input data files to create an arbitrary number of output data files using user-specified equations for the new data. The input files should have the same number of data points; excess points will be ignored. All operations are carried out on the ordinates. The abscissa values are assumed to be identical, and are taken from the last input file.

  dsc makes use of the Reverse-Polish-Notation expression evaluator from the program rpn.

• options:

  rpn_file

  
  Specifies the name of a file containing rpn expressions to be executed prior to processing.

  rpn_expression

  
  Specifies a rpn expression to be executed prior to processing.

  format

  
  Specifies a C-style format string for printing the data to the output file.

  independent_variable

  
  Specifies the name by which the independent variable values will be accessed in rpn expressions, as well as the name that will be placed in the output files. By default, this name is taken from the name of the abscissa in the last input file.

  variable

  
  Specifies a new variable, giving the file from which successive ordinate values will be read and the name of the variable. Any number of these options may appear.

  command

  
  Specifies a rpn expression to be executed during processing. The expression may use the independent variable, the variables created with variable arguments, the variables corresponding to preceeding result expressions, any variables into which values are stored by preceeding command arguments, and any variables defined in the setup files or expressions. Any number of these options may appear.

  result

  
  Specifies a quantity to be computed and output to a file, giving the name of the variable by which the quantity will be accessed in rpn expressions, the name of the file in which to place the data, and a rpn expression for the quantity. The expression may use the independent variable, the variables created with variable arguments, the variables corresponding to preceeding result expressions, any variables into which values are stored by preceeding command arguments, and any variables defined in the setup files or expressions. Any number of these options may appear.

  test

  
  Specifies a rpn expression returning a logical value. If given, the results for any step are placed in the output files only if the expression returns true. The test may use any and all variables defined by any of the preceeding options.

• processing sequence:
  The processing sequence for dsc is:
  1. Read and process the rpn file named in the RPN_DEFNS environment variable.
  2. Read and process the rpn file named in the rpn_file option, if given.
  3. Execute the rpn expression given with the first_rpn_expression option, if given.
  4. Read in data files and define variables as per variable options.
  5. Open and initialize ouput files as per result options.
  6. Loop over data points until any file is exhausted:
     1. Store the abscissa as the ``indepedent variable'' value.
     2. Load ordinates into the variables named in the variable options.
     3. Process command and result expressions in the order given.
     4. Write to output files as specified in the result arguments, but only if there is no test specified or if the test is true.
• examples:
  
  • Add two files, named input1 and input2, and placing the result in output1, but only if the value in the first file is greater than that in the second file.

    dsc -variable=y1,input1 -variable=y2,input2  
            -result=sum,output1,"y1 y2 +" -test="y1 y2 >"

  • Compute the product of a file with several Bessel functions:

    dsc -variable=y,input -independent_variable="x"  
            -result=yJ0,input_times_J0,"x 0 JN y *"  
            -result=yJ1,input_times_J1,"x 1 JN y *"

  • Compute the successive powers of the ordinate values in a file:

    dsc -variable=y,input  
            -result=y2,input-squared,"y y *"
            -result=y3,input-cubed,"y2 y *"
            -result=y4,input-pow4,"y3 y *"

• see also:

  
  add, mult, rescale.