Last month I published an article that included an interactive mathematical demonstration powered by Wolfram’s new CDF (Computable Document Format) player. These demonstrations work on many modern web-browsers including Internet Explorer 8 and Firefox 3.6. So, how do you go about adding them to your own websites?
What you need
- Mathematica 8.0.1 or above to create demonstrations. Viewers of your demonstration only need the free CDF player for their platform.
- A modern browser such as Internet Explorer 8, Firefox 3.6 or Safari 5.
- Basic knowledge of HTML, uploading files to a webserver etc. If you maintain a blog or similar then you almost certainly know enough
Our aim is the following, very simple, interactive demonstration.
If all you see is a static image then you do not have the CDF player or Mathematica 8 correctly installed. Alternatively, you are using an unsupported platform such as Linux, iOS or Android.
Step 1 – Create the .cdf file
Fire up Mathematica, type in and evaluate the following code. You should get an applet similar to the one above.
Manipulate[
Series[Sin[x], {x, 0, n}]
, {n, 1, 10, 1, Appearance -> "Labeled"}
]
Save it as a .cdf file called series.cdf by clicking on File->Save as — Give it the File Name series.cdf and change the Save as Type to Computable Document (*.cdf)
Step 2 – Get a static screenshot
Not everyone is going to have either Mathematica 8 or the free CDF player installed when they visit your website so we need to give them something to look at. So, lets give them a static image of the Manipulate applet. As a bonus, this will act as a place holder for the interactive version for those who do have the requisite software.
Open series.cdf in Mathematica and left click on the bracket surrounding the manipulate (see below). Click on Cell->Convert To->Bitmap. Then click on File->Save Selection As . Make sure you change .pdf to something more sensible such as .png
Don’t save your .cdf file at this point or it won’t be interactive. Re-evaluate the code again to get back your interactive Manipulate.
Here’s one I made earlier – series.png
Step 4 – Hide the source code
In this particular instance, I don’t want the user to see the source code. So, lets sort that out.
- Open series.cdf in Mathematica if you haven’t already and make sure that the Manipulate is evaluated.
- Left click on the inner cell bracket surrounding the Manipulate source code only and click on Cell->Cell Properties and un-tick Open
Step 5 – Hide the cell brackets
Those blue brackets at the far right of the Mathematica notebook are called the Cell brackets and I don’t want to see them on my web site as they make the applet look messy.
- Open series.cdf in Mathematica if you haven’t already
- Open the option inspector: Edit->Preferences->Advanced->Open Option Inspector
- Ensure Show option values is set to “series.cdf” and that they are sorted by category. Click on Apply.
- Click on Cell Options-> Display options and in the right hand pane set ShowCellBracket to False
- Click Apply
Before you save series.cdf ensure that the applet is interactive and not a static bitmap. If it isn’t interactive then click on Evaluation->Evaluate notebook to re-evaluate the (now hidden) source code. Also ensure that there is nothing but the applet anywhere else in the notebook.
Step 6 – Get interactive on your website
Upload series.png and series.cdf to your server. The next thing we need to do is get the static image into our webpage. Here’s what the HTML might look like
<img id="Series_applet" src="series.png" alt="Series demo" />
Obviously, you’ll need to put the full path to series.png on your server in this piece of code. The only thing that is different to the way you might usually use the img tag is that it includes an id; in this case it is Series_applet. We’ll make use of this later.
The magic happens thanks to a small javascript applet called the CDF javascript plugin. Version one is at http://www.wolfram.com/cdf-player/plugin/v1.0/cdfplugin.js and that’s the one I’ll be using here. Here’s the code which needs to be placed before the img tag in your HTML file.
<script src="http://www.wolfram.com/cdf-player/plugin/v1.0/cdfplugin.js"
type="text/javascript"></script><script type="text/javascript">// <![CDATA[
var cdf = new cdf_plugin();
cdf.addCDFObject("Series_applet", "series.cdf", 403,109);
// ]]></script>
The only line you’ll need to change if you use this for anything else is
cdf.addCDFObject("Series_applet", "series.cdf", 403,109);
where Series_applet is the id of the image we wish to replace and series.cdf is the cdf file we want to replace it with. The numbers 403,109 are the dimensions of the applet. These will not be the same as the .png file as the dimensions of the .cdf file are slightly larger. I used trial and error to determine what they should be as I haven’t come up with a better way yet (suggestions welcomed).
So that’s it for now. Hope this mini-tutorial was useful. Let me know if you upload any demonstrations to your own website or if you have any comments, questions or problems.
Update (6th June 2011)
Thanks to ‘Paul’ in the comments section, I have discovered that this mechanism won’t work for .cdf files that Wolfram deem are unsafe. According to Paul the definition of unsafe is as follows:
Dynamic content is considered unsafe if it:
- uses File operations
- uses interprocess communication via MathLink Mathematica Functions
- uses JLink or NETLink
- uses Low-Level Notebook Programming
- uses data as code by Converting between Expressions and Strings
- uses Namespace Management
- uses Options Management
- uses External Programs
