如何在codeigniter

Question

我在codeigniter中创建饼图。我的问题是它只显示一个值。我需要StockValuebyCost和StockValuebyPrice两个，根据我的代码，它只显示一个值StockValuebyCost，帮我如何显示StockValuebyCost和StockValuebyPrice。

MYmodel

   function getStock(){
    $this->db->select('sum(quantity * cost_price)As StockValuebyCost,
            sum(quantity * unit_price)As StockValuebyPrice');
    $this->db->from('items');
    $this->db->join('item_quantities', 'items.item_id = item_quantities.item_id');
        $this->db->where('deleted', 0);
       return $this->db->get()->result(); // Return the results in a array.
    }

MY Controller

function getdata() 
    { 
    $data = $this->home_model->getStock();
    $responce->cols[] = array( 
        "id" => "", 
        "label" => "Topping", 
        "pattern" => "", 
        "type" => "string" 
    ); 
    $responce->cols[] = array( 
        "id" => "", 
        "label" => "Total", 
        "pattern" => "", 
        "type" => "number" 
    ); 
    foreach($data as $cd) 
        { 
        $responce->rows[]["c"] = array( 
            array( 
                "v" => "StockValuebyCost", 
                "f" => null 
            ) , 
            array( 
                "v" => (int)$cd->StockValuebyCost, 
                "f" => null 
            )
        );

        }
    echo json_encode($responce); 
    }

我的观点js

// Load the Visualization API and the piechart package. 
google.charts.load('current', {'packages':['corechart']}); 

// Set a callback to run when the Google Visualization API is loaded. 
google.charts.setOnLoadCallback(drawChart); 

function drawChart() { 
  var jsonData = $.ajax({ 
      url: "<?php echo base_url() . 'index.php/home/getdata' ?>", 
      dataType: "json", 
      async: false 
      }).responseText; 

  // Create our data table out of JSON data loaded from server. 
  var data = new google.visualization.DataTable(jsonData); 

  // Instantiate and draw our chart, passing in some options. 
  var chart = new google.visualization.PieChart(document.getElementById('chart_div')); 
  chart.draw(data, {width: 700, height: 500}); 
} 

帮助我如何显示两个值