R E P O R T

"Vivian's polynomial plotter"

Contents Conception The Scenario Technical details-problems References - Bibliography

Conception
This is an exercise I did totally by chance :) I actually wanted to do something with EAI (External Authoring Interface). But, as I have Linux at home, I faced many difficulties to run VRML mostly form my machine. After spending hours on the web to find a descent VRML plugin, I realised that VRwave, VRweb and all the rest seemed far away from the ones that exist for Windows. Considering that I had already spent quite some time to find a good idea to implement, I stopped for a while and thought seriously to change my mind and do something else. And that's exactly what I did...

The only thing that I hadn't done yet, was Swing. Adding to it, that it is Hip :) and people like applets, I thought what the hell, let's have fun! Actually, I already had an idea of putting some swing components inside the project management of staf18 (mostly a progress bar). So, it was a very good opportunity to play with Swing and exercise myself.

Of course, like always, I started again looking for a good idea that can be also educative, like all my exercises for this diploma. Trying to figure out what could be graphic and also serious and educative and I came out with : graphs! The idea of implementing something that has to do with maths (how original for me :) seemed so perfectly nice that I started immediately.

I decided to make an applet from which a web surfer (hopefully a high school student) could manipulate some swing components, form a function and watch it's graph and how it changes by adjusting the coefficients of x.

As a conclusion, I strongly believe that this application can be a very educative tool for polynomial graphs. In my case, that I take a second degree polynomial, someone can immediately move only one slider and watch that:

• if it's the coefficient of x², the curve "opens" or closes,
• if it's the coefficient of x, the graph moves vertically along the Y axis following a curved trajectory and
• if it's the constant term, the graph moves vertically along the Y axis.

The scenario
My swing components are:

Function dynamic field:

Limits:

Sliders:

Canvas:

Technical details - problems
First problem was with VRML that there are no descent plugins for Linux. And the ones that exist are complicated to install with many problems.

With Swing now, one of the problems I had, was calculations with Java. In the beginning I wanted to make the plotter for five degree polynomials or even let the user to choose the degree, but I realised that it was an utopy. Even diminishing the degree to number three, I still have problems because Java is getting crazy every time that I choose some bigger numbers for limits or coefficients.

Another problem, that I face, is that my applet doesn't work as well as my application. With appletviewer works perfectly well, but as long as I change the main() method to init() for the applet, only the graph changes and the rest change only if I reload the page!

I would like to note down some details:

• calculations: I calculate the position of the axis and I transfer the coordinates to the current canvas.
• polylines: I create the graph with the use of the method drawPolyLine() that takes two arrays with x and y points and join them with a line.
• educative compliant: a high school student can watch the effects to the graph immediately by changing the limits and the coefficients. Such an application could be a suppliant tool to a teacher to explain the domain of graphs.
• simple interface: thanks to swing components the interface is quite ergonomic and the result quick.

References - Bibliography - Sites

• TECFA's Java Resources (especially for Swing)
• Fundamentals of JFC/Swing (By MageLang Institute)
• APPLETS (java.sun.com)
• JAVA PLUG-IN HTML SPECIFICATION