Monthly Archives: July 2015

Exploring Weibull distribution in TI Nspire

The graphing applet in TI Nspire is a great tool for visualizing Weibull distribution, by adjusting the variable sliders for shape and scale parameters. Cumulative distribution is easily obtained by the Integral function under analyze graph feature.

weibull

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Nelder-Mead algorithm on the TI-84 Plus SE

This mean nothing more than to prove that implementing the Nelder-Mead algorithm on the TI-84 is possible. In reality, the time it will take for a TI-84 Plus SE to arrive a solution for any practical non-linear problem renders this somewhat a last resort option. That is, in the absence of any modern computer or even a decent mobile phone 🙂

The program is implemented in the native TI-Basic, which is ported from the program for the same problem previously done on TI Nspire and Casio fx-9860GII. It took some efforts to port the program as the resources on the TI-84 is comparatively limited. For example,variable names are also restricted to single character, but thanks to list, things are easier.

With the availability of the new generation TI-Connect software, the Program Editor has returned and this tool greatly helped programming the Nelder-Mead on TI-84. Although unlike the more advanced Nspire Software which is able to run the program on PC instead of having to download the program to the TI-84 every time, editing TI-Basic in PC with a full keyboard and full screen is way more comfortable than to doing so on the calculator. The new TI-Connect CE PC software looks really nice.

ti84+nelder-mead1

Screens of the actual program running on a TI-84 Plus Pocket SE. The equation to solve is the Rosenbrock function of f(x,y) = (a-x)^2 + b(y-x^2)^2, using a=1 and b=100.

ti84+nelder-mead2

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The TI-84 Plus Pocket SE took 12 minutes to complete, while its big brother TI Nspire took only 22 seconds.