scilab&
(in X terminal) Another large and sophisticated system for numerical computing, somewhat resembling "matlab", but with a rather clampsy graphical interface. Don't even try it unless you have rather sophisticated math needs else you won't appreciate it. It is included on RH7.0 "powertools" CD. The hompage is http://www-rocq.inria.fr/scilab/
A silly example session showing some matrix algebra. My input is shown bold.
-->a=[1 1 1;2 3 4]
a =
! 1. 1. 1. !
! 2. 3. 4. !
-->b=[1 1; 2 2;3 3]
b =
! 1. 1. !
! 2. 2. !
! 3. 3. !
-->c=a*b
c =
! 6. 6. !
! 20. 20. !
-->d=inv(c)
d =
1.0E+14 *
! 11.258999 - 3.3776997 !
! - 11.258999 3.3776997 !
-->
head -c 8 /dev/random
cat /dev/random | od
cat /dev/urandom | memencode
(3 commands.) Examples on how to generate random characters on the Linux command line by reading from the device "random" or "urandom". The first command produces approximately 8 characters by reading from the device "random", which generates high quality (difficult to predict) random numbers. It will become slow once the "entropy" on your computer is exhausted (e.g., when producing lots of random characters). The solution then is to wait or type something on the keyboard, move your mouse, switch the terminal, make your hard drive to read or write, etc., to generate more random noise ("entropy"). The second command keeps producing random characters, but displays them as octal numbers (using the "octal dump", od, filter). It has to be interrupted with <Ctrl><c>. The third command uses the device "urandom", which is faster then "random" when generating lots of random characters. But when the system enthropy is low, the randomness of its output from "urandom" might be compromised, yet it probably is still good for all but most demanding applications. The output is filtered to the mime format (the Internet mail-oriented 7-bit encoding standard) so it is all printable ASCII. The detailed description of the theorry and implementation of the Linux algorithm for generating the random numbers can be found in the source code file://usr/src/linux/drivers/char/random.c on your Linux system.
factor 10533858466222239345
Find all the prime factors of an integer number. Factors of an integer are numbers by which the integer is divisible without a remainder. For example, the factors for 6 are: 1, 2, 3, and 6.
R
A programming language / environment for advanced statistical computing. Type "quit()" to exit.
gnuplot
Utility for creating graphs and plots. Very good for non-interactive (batch) work, but not very simple for interactive use. A good introduction to gnuplot can be found at http://www.duke.edu/~hpgavin/gnuplot.html.
