i am using phplot to plot a graph in a web page, and i have the following code for it,

```
   <?php
     //Include the code
    require_once 'C:/xampp/htdocs/phplot-6.1.0/phplot.php';

     //Define the object
     $plot = new PHPlot();

    //Define some data

     $example_data = array(
     array('a',3),
     array('b',5),
     array('c',7),
     array('d',8),
     array('e',4),
     array('f',6),
      array('g',7)
      );
     $plot->SetDataValues($example_data);

     //Turn off X axis ticks and labels because they get in the way:
     $plot->SetXTickLabelPos('none');
     $plot->SetXTickPos('none');

      //Draw it
      $plot->DrawGraph();
       ?>

```

i don't want to define the data as in $example\_data, but i want to read or upload this from an external file like txt or json, please suggest how to achieve this and what can be the type of the external file to be uploaded ?