I'd like to note some differences in using charts of both kinds. And I think it makes a very big difference.
I'll call any image-based chart by "static chart". It's just a static image. Example of such charts are those generated by Google Image Charts (they now also have new, interactive charts), or RRDtool. Show below is an example of a static chart; in this example, generated by Google:
Pros and cons of static charts
- Images can be viewed on any graphical platform. Browsers, email clients, cell phones, whatever.
- Self contained: chart image, legend, scales: all in one image.
- As such, easy to move around.
- Are safe to use.
- Images are fuzzy. Is the com_replace_psec really 0? Maybe it's 0.1? A larger value can make lower values hard to tell.
- Images are inaccurate: the colors can lie. The red and green lines showing are hard to tell apart. The red is painted above the green. Data gets "lost".
- They do not zoom (one needs to regenerate larger image)
- Unless encoded with base64, HTML pages which include images need to link outside.
- In the particular case of Google Charts, one is limited to 2K length URL. Trust me, it's a big limitation! (PS, Google now support POST method to allow for up to 16K. But... it's a POST method...)
- In the particular case of Google Charts, one must have an internet connection.
- In the particular case of Google Charts, one must submit data to Google.
The above chart is generated with dygraphs. Since it is embedded within my WordPress page, the layout is affected by that of my theme. Take a look at this example page to see similar charts outside this blog site (Internet Explorer users: Maxmimize/minimize button will not work well for now. And, may I suggest Mozilla Firefox?)
Pros and cons of interactive charts
- Can present you with exact values. No more doubt about the com_replace_psec values.
- Can allow for zoom in, zoom out.
- Charts are not necessarily self-contained, in terms of the chart entity With Flash charts (e.g. Fusion Charts) this works. But in the above, the legend and scales are outside the image. As such, they cannot be just moved around.
Interactive charts are cool!
I'm now integrating dygraphs into mycheckpoint (How nice it is to work with BSD & MIT licenses!). Though I may later switch to flot, interactive charts will be the next standard charting way in mycheckpoint. I will continue supporting static Google Charts, as follows from the above pros and cons list.