The show_data function reads the hsoutput.dat file, which contains interpolated query output from the Cascade Historian, retrieved by the InterpolatorSettings.get_data method. This function modifies the data slightly as necessary, and puts it into the text widget.

   /*--------------------------------------------------------------------
    * Function:    show_data
    * Returns:     t or nil
    * Description: Shows interpolated query results from the Cascade Historian
    *              in the text widget and plots the results in the CwGraph widget.
    *------------------------------------------------------------------*/
   function show_data(txt_wgt, int_set, parent, button, datalist, minmaxlist)
   {
     local start_time, infile, line, string_list, line_ret;
     local x_is_time, x_min, x_max, y_min, y_max, x_list, y_list;
     local outstring = open_string ("");
     
     x_list = car(datalist);
     y_list = cadr(datalist);
     txt_wgt.text_string = "";
     start_time = find_midnite();
     
     if (int_set.fn == "NoInterpolator"  || int_set.fn == "Periodic")
       {
         x_is_time = t;
         txt_wgt.text_string = "Query results: \n     Time         Y History\n";
       }
     else
       {
         x_is_time = nil;
         txt_wgt.text_string = "Query results: \nX-hist / Y-hist\n";
       }
     
     infile = open("/tmp/cogentdemo/hsoutput.dat", "r");
     if (infile)
       {
         line = nil;
         while(line != _eof_)
           {
             line = read_line(infile);
             line_ret = "";
             if (line != "Unexpected end of file")
               {
                 if ((strstr(line,"#") != -1))
                   {
                     writec (outstring, line);
                     read_line(infile);
                     read_line(infile);
                   }

If the first character in the first line of output is "#", this means there was no data available. If this is the case, the .get_data method will have printed two dummy data lines into the hsoutput.dat file. These two lines must be read now, so that they will not get inserted into the text widget by the rest of this function. Hence we put in two extra Gamma read_line calls.

                 else
                   {
                     string_list = string_split(line, " ", 2);
                     if (x_is_time)
                       {
                         line_ret = string(number(car(string_list)) - start_time,
                                           " ", cadr(string_list),"\n");
                       }

Valid data in the hsoutput.dat file comes in two space-separated columns of numbers. If the numbers in the first column are time values (created using NoInterpolator or Periodic for the interpolator), this function recalculates each value to the number of seconds after midnight. This makes the data easier to read, and makes a better display in the plot.

                     else
                       {
                         line_ret = string(number(car(string_list)),
                                           "   ", cadr(string_list),"\n");
                       }
                     writec (outstring, line_ret);
                   }
               }
           }
         
         txt_wgt.text_string = string(txt_wgt.text_string, string_file_buffer(outstring));
         
         if(x_list && y_list && minmaxlist != nil)
           {
             if (x_is_time)
               {
                 x_min = caar(minmaxlist);
                 x_max = cadar(minmaxlist);
               }        
             else
               {
                 x_min = floor(caar(minmaxlist));
                 x_max = ceil(cadar(minmaxlist));
               }
             
             y_min = floor(caadr(minmaxlist));
             y_max = ceil(car(cdadr(minmaxlist))) + 1;
             
             PtSetParentWidget(parent);
             
             make_graph(x_min, x_max, y_min, y_max,
                               x_list, y_list, int_set.dbflag);
           }          
         else
           txt_wgt.text_string = string("Sorry, there was an error retrieving\n",
                                        "data from the Cascade Historian.");
         close(infile);
       }
   }
   

After extracting the minimum and maximum values for the data from the minmaxlist, we call the make_graph function to plot the data.