Plotter: a tool to create bitmap charts for the web
In the past couple of months, I have been busy maintaining a blog for OECD: Factblog.
The idea is to illustrate topics on which we work by a chart which we’ll change regularly. So in order to do that, I’d have to be able to create charts of publishable quality.
Excel screenshots: not a good option
There are quite a few tools to create charts on the net. Despite this, the de facto standard is still a screenshot of Excel, a solution which is even used by the most reputable blogs.
But alas, Excel is not fit for web publishing. First, you have to rely on Excel’s choice of colours and fonts, which won’t necessarily agree to those of your website. Second, you can’t control key characteristics of your output, such as its dimensions. And if your chart has to be resized, it will get pixelated. Clearly, there is a better way to do this.
How about interactive charts?
Then again, the most sensible way to present a chart on the web is by making it interactive. And there is no shortage of tools for that. But there are just as many issues.
Using java cause two problems. First, the hiccup caused by the plug-in loading is enough to discourage some users. Second, it may not be understood well by readers:
And it’s futile to believe that readers will read blogs from their home pages. So if all readers can’t show it well it’s a show-stopper.
A tool to create good bitmap charts
Here’s how it works.
when you unzip the files, you have a file called “mychart.txt” which is a set of parameters. Edit the file according to the instructions in “instructions.txt” to your liking, then launch the tool (plotter application). It will generate an image, called “mychart.png”.
The zip files contain the source code, which is also found here on my openprocessing account.
With my tools, I wanted to address two things. First, I wanted to be able to create a chart and to have a precise control of all of its components, especially the size. In Excel, by contrast, it’s difficult to control the size of the plotting area, or the placement of the title – all of this things are done automatically and are difficult to correct (when it’s possible). Second, I wanted to be able to create functional thumbnails.
If you have to create smaller versions of a chart from a bigger image, the easiest solution is to resize the chart using an image editing software. But that’s what you’d get:
But what if it were just as easy to re-render the chart in a smaller size, than to resize it with an external program? My tool can do that, too.
Here’s a gallery of various charts done with the tool. The tool supports: line charts, bar charts (both stacked and clustered), dots charts and area charts. No pie charts included. It’s best suited for simple charts with few series and relatively few data points.
I hope you find it useful, tell me if you do and let me know if you find bugs.