Building array and formatting JSON for Google Charting API

Question

I am working on a project where I am making use of the Google Charting API and I want to populate the chart using json to build the data table.

As a test I am trying to build a simple array before I try and do it with dynamic data from a database but I am having a problem getting the json in the correct format.

In the google documentation it says the json content should be in the following:

{
  "cols": [
        {"id":"","label":"Topping","pattern":"","type":"string"},
        {"id":"","label":"Slices","pattern":"","type":"number"}
      ],
  "rows": [
        {"c":[{"v":"Mushrooms","f":null},{"v":3,"f":null}]},
        {"c":[{"v":"Onions","f":null},{"v":1,"f":null}]},
        {"c":[{"v":"Olives","f":null},{"v":1,"f":null}]},
        {"c":[{"v":"Zucchini","f":null},{"v":1,"f":null}]},
        {"c":[{"v":"Pepperoni","f":null},{"v":2,"f":null}]}
      ]
}

I am calling a function which returns the json code.

Below is how the function is called

print json_encode(test());

and the test function is

function test()
{
    $array = array();
    $array['cols'][] = "20-01-13";
    $array['cols'][] = "21-01-13";
    $array['cols'][] = "22-01-13";
    $array['rows'][] = 22;
    $array['rows'][] = 26;
    $array['rows'][] = 12;

    return $array;
}

The javascript that generates the chart is as follows

<script>
            google.load('visualization', '1', {'packages':['corechart']});

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

            function drawChart() {
                 var jsonData = $.ajax({
                 url: "loadGraph.php",
                 dataType:"json",
                 async: false
                }).responseText;

                var data = new google.visualization.DataTable(jsonData);

      // Instantiate and draw our chart, passing in some options.
      var chart = new google.visualization.PieChart(document.getElementById('lineGraph'));
      chart.draw(data, {width: 400, height: 240});
            }
        </script>

When I echo the json it is being returned in the following format

{"cols":["20-01-13","21-01-13","22-01-13"],"rows":[22,26,12]}

and if I try and use this for the datasetfor the google chart I get the following message

Cannot read property of '1' of undefined

I am only building a simple line chart which will just contain a date along the x axis and a count of how many times something happened on that date along the y axis.

How do I nee to build up the array to get it in the correct format for the google api chart.

Thanks for any help you can provide.

There is nothing obviously wrong with the data as you have shown it. The problem may be in how you use it, so you should provide a more complete example. Set up a jsfiddle that demonstrates the problem. — dlaliberte
– dlaliberte, Commented Jun 22, 2013 at 14:56
The json being returned by your php code is obviously not the same as what you expect to output, and what the chart expects as data. So this is a problem with your php test() function that generates the wrong structure to start with. The error from google charts is rather confusing, but beside the point. Sorry I can't help you with the php code. — dlaliberte
– dlaliberte, Commented Jun 23, 2013 at 14:19

Fabi · Accepted Answer · 2013-06-24 22:39:25Z

7

+50

You need to specify the parameter type for cols. Refer to Google Charts JSON Format

Your PHP code should look similar to:

function test()
{
    $array['cols'][] = array('type' => 'string');
    $array['cols'][] = array('type' => 'string');
    $array['cols'][] = array('type' => 'string');

    $array['rows'][] = array('c' => array( array('v'=>'20-01-13'), array('v'=>22)) );
    $array['rows'][] = array('c' => array( array('v'=>'21-01-13'), array('v'=>26)));
    $array['rows'][] = array('c' => array( array('v'=>'22-01-13'), array('v'=>12)));

    return $array;
}

print json_encode(test());

Your json code would look more like:

{
  "cols": [
    {"type": "string"},
    {"type": "string"},
    {"type": "string"}
    ],
  "rows": [
    {"c":[{"v":"20-01-13"}, {"v":22} ]},
    {"c":[{"v":"21-01-13"}, {"v":26} ]},
    {"c":[{"v":"22-01-13"}, {"v":12} ]}
  ]
}

edited Jun 24, 2013 at 22:39

answered Jun 24, 2013 at 21:41

Fabi

9737 silver badges18 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Boardy Over a year ago

Thanks, but I know what format the JSON needs to be in, I included that in the question, the problem is I am not sure how to create the array so when it is json encoded it is in the correct format

Boardy Over a year ago

No sorry, SO, didn't give me the notification that it was updated. I'll give it a try tonight after work and get back to you

Boardy Over a year ago

Thanks so much this does work. The only thing I don't understand is what the "c" and "v" means within the array.

Fabi Over a year ago

follow the reference to Google Charts JSON Format in the answer, it explains all the variables there

Zafer Over a year ago

There is a small problem in code. It should be like that: function test() { $array['cols'][] = array('type' => 'string'); $array['cols'][] = array('type' => 'number'); $array['rows'][] = array('c' => array( array('v'=>'20-01-13'), array('v'=>22))); $array['rows'][] = array('c' => array( array('v'=>'21-01-13'), array('v'=>26))); $array['rows'][] = array('c' => array( array('v'=>'22-01-13'), array('v'=>12))); return $array; }

vard · Accepted Answer · 2016-02-08 09:51:57Z

This may come a bit late but anyway, here's what worked for me (needed to create a barchart).

Get the server code to return the json string representing an array e.g. something like:

[{
  "score": 12,
  "subject": "Computer Graphics"
}, {
  "score": 65,
  "subject": "Entreprenuership"
}, {
  "score": 82,
  "subject": "C++Programming"
}]

Parse the string using eval() or JSON.parse() to get the JavaScript object.
```
var chartData = JSON.parse(jsonStringFromServer);
```

Create a DataTable object as such:

var dTable = new google.visualization.DataTable();

Add columns to the dataTable :

dTable.addColumn('string','Subject'); 
dTable.addColumn('number','Score'); 
//more columns if needed...

Loop through the javascript array (chartData) and for each object in the array, add a new row to the dataTable:

for(i=0;i<chartData.length;i++){
    var currentObj = chartData[i];
    dTable.addRow([currentObj.subject,currentObj.score]);
}
//set options for the chart e.g title, width etc
// create the chart ...

GoldenTabby · Accepted Answer · 2013-06-26 12:49:59Z

0

it should be like:

array(10) {
  [0]=>
  array(2) {
    [0]=>
    string(2) "en"
    [1]=>
    int(104)
  }
  [1]=>
  array(2) {
    [0]=>
    string(0) ""
    [1]=>
    int(70)
  }
  [2]=>
  array(2) {
    [0]=>
    string(2) "zh"
    [1]=>
    int(13)
  }
  [3]=>
  array(2) {
    [0]=>
    string(2) "ru"
    [1]=>
    int(10)
  }
  ...

then

var data = google.visualization.arrayToDataTable(<?php echo json_encode($our_array); ?>);

var chart = new google.visualization.PieChart(document.getElementById('someId'));
chart.draw(data, options);

answered Jun 26, 2013 at 12:49

GoldenTabby

2202 silver badges13 bronze badges

Collectives™ on Stack Overflow

Building array and formatting JSON for Google Charting API

3 Answers 3

5 Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

5 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related