Scatter chart library - moving to Flot

After playing with Open Flash Chart 2 trying to make interactive scatter plot, I've found severe glitches that popped up during prototyping. Library worked quite well for standard line and bar charts. But for my specific scatter chart I realized that:

• I have to use hacks to provide 0,0 origin based XY axes (OK I could just use standard left/bottom axes)
• there are problems with larger scale values (I didn't checked exactly but values in range to 10000 rendered OK, somewhere above it is some kind of limitation)
• problem with grid rendering for values in less than zero range
• OFC can't parse scientific notation values (data number formatting is a must)
• some minor problems that could be solved by chart tuning and hacking ranges etc.
• after playing with OFC stable version I've checked last trunk version that worked much better

I summed all problems and thought about potential extendability problems and tried to move to library based on HTML Canvas object. One of the simplest and most mature projects is Flot. It has all required features, including interaction. The only problem I found was rendering under IE using Excanvas emulation object. Standard stable Flot version doesn't work well under IE8. Charts were drawn although without data points. After checking project issues list, I've found that some problems where resolved by using newer JQuery and Excanvas library. I've tried to run Flot from trunk version, and my IE8 problems were solved. As a extra newer Flot version contains more interesting plugins like navigation. BTW maybe it's time to publish next Flot stable version in downloads section. The only disadvantage of that solution is forcing IE users to accept running Excanvas security policy.

Long break and back to work

It was long time ago from last post. I had real "without thinking about work" vacation. Mostly cycling and resting with family in small house near lake shore. I've been using Internet mostly for communication and weather forecasts. After back to work I had to catch up to meet approaching deadlines. So sorry about not giving any signs of life for a long time.

Choosing scatter chart library for web application

So I definitely know that I have to make web based UI for medical diagnostic application. It's not so complicated as I initially though. It is a kind of scatter chart that has to display delivered XY data and use as reference some kind of meta data like description, database id etc. Basic functionality of that module is adding and editing points. It should be somehow interactive - like has clickable points that can fire various events. Graph zooming is also needed.

There are articles with list of interesting solutions: 13 useful graphing solutions, 10 Free Chart Scripts. I reviewed few charting libraries that can be divided into three categories:

• HTML canvas charts
• Java applets
• Flash based charts

There where also other interesting ideas like SVG based interactive chart, or image chart with imagemap and added DHTML tricks, but still without enough support and needed writing more code.

Needed charting solutions should be lightweight so I thought about html canvas drawing, but unfortunately there are serious IE issues - It does not implement such feature, so excanvas ActiveX is used not always successfully (new IE changes are breaking excanvas functionality).

Another good choice from point of customization and extending functionality is Java applet based on JFreeChart, or lighter jchart2d library. Using Java applet was tempting. I made some serious applet work some time ago so I had to make some user experience tests of deploying UI as applet. The large group of users has no technical computer background, and can be confused about accepting prompts for Java installation (Java is not preinstalled with system in here), waiting for runtime download and finally for applet initializing. That may cause serious problems with acceptance tests.

So I tried Open Flash Chart 2- the nice flash based chart library. It has fixed but all basic features I need. Flash player is king of the browsers (large deployments ratio) today. That and smaller than Java's runtime should cause less problems with runtime installation. It has wrapper libraries in most popular programming languages including Java. I have choose third party jofc2 library for quite easy integration with code sample from Open Flash Chart and Wicket example.

Open Flash Chart has enough javascript interface, to dynamically change data, graph style, add tooltips and script onclick events on data points. It has no direct zooming support but can be implemented as changing chart properties by adding external scripted controls. Redrawing after data delivery is fast also.

Near future brings even more choices like Silverlight, improved Applet/JavaFX runtime or adoption of canvas like solutions.

Further reading:
Scatter chart library - moving to Flot
Looking for simple python chart library

Rich GUI dilemma - web or desktop application?

I'm planning additional visualization tools for diagnostic system. The have "additional" role - because will be scarcely used only by expert users. It's a kind of fancy interactive scatter plot with plenty of displaying options including simple data transformations.

Primarily I thought about it as a desktop application. But I when I get initial requirements it seemed that there is no much functionalities and it could be written as module of already existing web application for data gathering.
I have to gather more details , because now I have to guess future boundaries of that part of the system.

The basic pros and cons array:

	Pros	Cons
Web application	- its web application so you need only web browser (maybe Java or Flash runtime automatically downloaded by browser)- easy deploying - better (seamless) integration with the rest of the (web) system	- possibly low client performance depending on used technology
Desktop application	- established for rich GUI - more computational power to use on client side (really?) - targeted for more functionality "richness"	- target client system dependence (but I know that 99% of users uses Windows platform) - loose integration with the rest of web based system (deployment architecture allows it)

Reviewed technologies and solutions:

• Java desktop app
• Java applet
• GWT application
• YUI components
• flash components

Final choice depends on the range of features, and final users preferences. Web version seems more performance constrained - but there are many technological solutions that make that choice as good as its desktop counterpart. At that point there are very little differences between web or desktop deployment outcomes. Nowadays buzz is "web is the future". I have to make my choice based on economic assumptions.

The best programming language 2 - Simple case tale

The University needed temporary solution for generating list of quiz questions, chosen randomly from data prepared in structured text file. The scope of application was nothing comparing to "Enterprise Systems", so I treated it as a kind of entertaining enterprise.

The core characteristics were:

• simple logic
• UI forms for getting parameters from user
• printable or saveable formatted questions list
• low burden installation and use (get it on pendrive or download ready to use).
• main constraints: short time and possibly low cost.

I started looking for similar open source products, but not found needed functionality. So when I checked myself for Not Invented Here syndrome, I started thinking about custom solution.

There were many ways of implementation. I thought about preparing windows exe file with included required dependencies (no installing additional Java, .Net, Python or other runtime).
I started playing in "prototyping with Python"- it was fun and things were going smoothly. But I stopped before making UI. Plain old console was "too lame" for final users, so I planned GUI with TkInter included by default in python installation to avoid porting to windows executable problems.

I get core set of functionalities, but user interface still was barely specified. Then I get many additional requests about "last minute" changes in UI forms (and probably not the last). The second "economic" option was to implement the whole application in Java Script and HTML running under web browser. Every computer has web browser suitable to run that kind of application so there are almost no installation and portability issues. Implementation time should be short too. To speed up things I have changed data format from flat file of records into JSON structure. Porting logic was fast too. The most time took me making forms working.

First version was not so fancy and needed some GUI tweaking like formatting, changing labels and headers. In a case of any further UI changes other people knowing HTML could make fixes instantly. The extra feature was possibility of "deploying" the little application on a web server as HTML page. Saving result to file wasn't working directly. Making it really automatic needed interacting with browser security policies for access to local file system. We decided that it will be still usable if user use copy-paste technique, and place formatted result in external text editor. The default usage was printing questions on paper so nobody saw problem there.

Everything is working as designed, and shows that web browser should be treaded as good platform for small applications. Sometimes little prototyping gives better insight on a whole system.