code: public void writeScriptImportingDataFrame(Engine engine, Writer writer,
              InputVariable a, InputVariable b, String dataFramePath,
              List<OutputVariable> outputVariables) throws IOException {
          writeScriptHeader(writer, engine);
  
          writer.append("engine.fldFile = \"" + dataFramePath + "\"\n");
          writer.append("if (require(data.table)) {\n"
                  + "    engine.df = data.table::fread(engine.fldFile, sep=\"auto\", header=\"auto\")\n"
                  + "} else {\n"
                  + "    engine.df = read.table(engine.fldFile, header=TRUE)\n"
                  + "}\n");
          writer.append("\n");
  
          writeScriptPlots(writer, a, b, outputVariables);
      }
docs: Writes an R script plotting multiple surfaces based on a manually imported
  data frame containing the data for the two input variables on the output
  variables.
  
  @param engine is the engine to export
  @param writer is the output where the engine will be written to
  @param a is the first input variable
  @param b is the second input variable
  @param dataFramePath is the path where the data frame should be located
  (the path will not be accessed, it will only be written to script)
  @param outputVariables are the output variables to create the surface for
  @throws IOException if any error occurs upon writing on the writer