rhl35.htm

linux的初学电子书

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<FONT SIZE=4 COLOR="#FF0000"><B>More Information on Scilab</B></FONT></CENTER></H4>

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<P>The documentation for the Scilab application is available from <A HREF="tppmsgs/msgs1.htm#105" tppabs="ftp://ftp.inria.fr/">ftp.inria.fr</A> in the /INRIA/Projects/Meta2/Scilab/doc directory. It contains a PostScript document called intro.ps which contains the user's manual titled 
Introduction to Scilab. Take time to read this manual carefully.

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<FONT SIZE=5 COLOR="#FF0000"><B>Pari</B></FONT></CENTER></H3>

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<P>The Pari package is useful for doing symbolic mathematical operations. Its primary features include an arbitrary precision calculator, its own programming facilities, and interfaces to C libraries.

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<FONT SIZE=4 COLOR="#FF0000"><B>Where To Get Pari</B></FONT></CENTER></H4>

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<P>To get Pari, use the FTP site <A HREF="tppmsgs/msgs1.htm#107" tppabs="ftp://megrez.math.u-bordeaux.fr/">megrez.math.u-bordeaux.fr</A>, and from the /pub/pari/unix directory get the gplinux.tar.gz file. The binaries may not work with a later version of Linux because the binaries are 
built with older versions of shared libraries. If you have a newer version of Linux than the one supported by Pari, either you can edit the sources yourself or wait until the authors of Pari catch up. Sorry.

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<P>With the version of Linux on the CD-ROM, you need to compile your own version of Pari. The source files are in the pari-1.39.03.tar.gz file. The source tar file unpacks into three directories: src, doc, and examples. You will find the examples very 
useful indeed.

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<P>To compile the sources, run the Makemakefile command in the src directory. When creating this version, remove the definition of the option -DULONG_NOT_DEFINED from the CFLAGS macro in the newly created Makefile. Then type make at the prompt. Be prepared 
to wait awhile for this package to compile.

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<FONT SIZE=4 COLOR="#FF0000"><B>Running Pari</B></FONT></CENTER></H4>

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<P>After you have compiled the source files for Pari, type gp at the console prompt. Your prompt will be a question mark (?). Start by typing simple arithmetic expressions at this prompt. You should be rewarded with answers immediately. Let's look at the 
following sample session:

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<FONT COLOR="#000080">? 4*8

%1 = 32

? 4/7*5/6

%2 = 10/21</FONT></PRE>

<P>The answer was returned to us in fractions. To get real numbers, introduce just one real number in the equation. You will then get the answer as a real number. The percent signs identify the returned line numbers.

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<FONT COLOR="#000080">? 4.0/7 * 5/6

%3 = 0.4761904761904761904761904761</FONT></PRE>

<P>To set the precision in number of digits, you use the ?\precision command. The maximum number of digits is 315,623, a large number for just about all users. For a modest precision of 10 digits to the right of the decimal point, use

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<FONT COLOR="#000080">?\precision = 10

precision = 10 significant digits

? 4.0/7*5/6

%4 = 0.47619004761</FONT></PRE>

<P>You can even work with expressions, as shown in the following example:

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<FONT COLOR="#000080">? (x+2)*(x+3)

%5 = x^2+5*x + 6</FONT></PRE>

<P>You can assign values to variables to get the correct answer from evaluating an expression.

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<FONT COLOR="#000080">? x = 3

%6 = 3

? eval(%5)

%7 = 60</FONT></PRE>

<P>This is not where the power of Pari ends, though. You can factor numbers, solve differential equations, and even factor polynomials. The FTP site for Pari contains a wealth of information and samples. See megrez.math.u-bordeaux.fr. Also, the examples 
and docs directories contain samples and the manual to help you get started.

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<FONT SIZE=5 COLOR="#FF0000"><B>Using LISP-STAT</B></FONT></CENTER></H3>

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<P>For statistical computing, consider using LISP-STAT. Written by Luke Tierney at the University of Minnesota, LISP-STAT is a very powerful, interactive, object-oriented LISP package.

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<FONT SIZE=4 COLOR="#FF0000"><B>Where To Get LISP-STAT</B></FONT></CENTER></H4>

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<P>The LISP-STAT package is available from <A HREF="tppmsgs/msgs1.htm#108" tppabs="ftp://ftp.stat.umn.edu/">ftp.stat.umn.edu</A> in the /pub/xlispstat directory. Get the latest tar file version you can&#151;currently, xlispstat-3-44.tar.gz. In order to build this file you need the dld 
library for Linux. This dld library is found in <A HREF="tppmsgs/msgs0.htm#71" tppabs="ftp://tsx-11.mit.edu/">tsx-11.mit.edu</A> in the /pub/linux/binaries/libs directory as dld-3.2.5.bin.tar.gz. Install this dld library in the /lib directory first.

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<FONT SIZE=4 COLOR="#FF0000"><B>Running xlispstat</B></FONT></CENTER></H4>

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<P>At the command prompt in an Xterm, type xlispstat. You will be presented with a &gt; prompt. Type commands at this prompt. For example, to multiply two matrices together, use the command:

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<PRE>

<FONT COLOR="#000080">&gt; (def a (matrix '(3 3) '(2 5 7 1 2 3 1 1 2)))

A

&gt; (def b (matrix '(3 1) '(4 5 6)))

B

&gt; (matmult a b)

#2A((75.0) (32.0) (21))</FONT></PRE>

<P>The variables in LISP-STAT are not case-sensitive. Note the single quote (') before the list of numbers for the matrix. If you omit the quote, the list will be evaluated and replaced with the result of the evaluation. By leaving the single quote in 
there, you are forcing the interpreter to leave the list in its place.

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<P>Let's try solving a simple set of linear equations using LISP-STAT. The following would be a simple example to solve:

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<FONT COLOR="#000080">3.8x + 7.2y = 16.5

1.3x - 0.9y = -22.1</FONT></PRE>

<P>The following script would set up and solve this linear equation problem:

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<FONT COLOR="#000080">&gt; (def a (matrix '(2 2) '(3.8 7.2 1.3 -0.9)))

A

&gt; (def b (matrix '(2 1) '(16.5 -22.1)))

B

&gt; (matmult (inverse a) b)

#2A((-11.288732394366198) (8.249608763693271))</FONT></PRE>

<P>You can do other math operations on lists of numbers as well. See the following example for calculating the mean of a list of numbers:

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<FONT COLOR="#000080">&gt; (def sm (list 1.1 2.3 4.1 5.7 2.1))

SM

&gt; (mean SM)

3.06</FONT></PRE>

<P>There are many plotting functions available for LISP-STAT. For plotting one variable, try the function plot-function. For (x,y) pairs of numbers, use the plot-lines function. For a function of two variables, use the spin-function. For 3-D plots, use the 
spin-plot function.

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<P>Plots are not limited to lines. You can do histograms, planar plots, and so on. See the help pages for details on specifics of how to generate these plots. Two or more plots can be linked together so that changes in one set of data can be reflected in 
another. You can add points to a plot using the add-points function. For reconfiguring how the points are displayed, you can send commands to the plot windows. Plots can be linked together to enable more than one view of the same data.

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<a href="35rhl02.gif" tppabs="http://202.113.16.101/%7eeb%7e/Red%20Hat%20Linux%20Unleashed/35rhl02.gif">Figure 35.2 A Histogram sample</A></B>

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<P>Each plot is displayed in an X window. You can move the mouse cursor over a point, and it will echo back a value for you.

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<P>To get help on this system, use the help command. The help documentation for this command should be visible. If nothing shows up, check the environment variables to see if the binaries are in the PATH.

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<a href="35rhl03.gif" tppabs="http://202.113.16.101/%7eeb%7e/Red%20Hat%20Linux%20Unleashed/35rhl03.gif">Figure 35.3 Sample of using EIGEN-VALUES</A></B>

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<FONT SIZE=5 COLOR="#FF0000"><B>A Last Note</B></FONT></CENTER></H3>

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<P>For simple math operations involving spreadsheets, you can always use the xspread program provided with the X package. (The CD-ROM at the back of the book has version 2.1.) For more powerful spreadsheet functions, you might want to resort to a 
commercial spreadsheet package and take advantage of its support, too. The XESS spreadsheet is available for Linux from Applied Information systems, [phone] or <A NAME="I2"></A><A HREF="tppmsgs/msgs1.htm#111" tppabs="http://www.ais.com/Xess">http://www.ais.com/Xess</A>. You can 
share data between spreadsheets, or use the API to develop and have access to a full suite of math functions available on spreadsheets that run under DOS or UNIX.

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<P>Wolfram Research has released its Mathematica program for Linux. The Mathematica package has extensive numeric and symbolic capabilities, 2-D and 3-D graphics, and a very large library of application programs. With an additional feature called MathLink, 
you can exchange information between other applications on a network. You can get more information about Mathematica from <A HREF="mailto:[e-mail]">[e-mail]</A> or <A HREF="tppmsgs/msgs1.htm#112" tppabs="http://www.wri.com/">http://www.wri.com</A>.

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<FONT SIZE=5 COLOR="#FF0000"><B>Summary</B></FONT></CENTER></H3>

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<P>You have several options when it comes to performing mathematical operations or writing such applications under Linux. You can either write the code yourself using C, FORTRAN, or other available languages&#151;or you can use a package. If you are 
familiar with MATLAB, consider using Scilab. For regular expressions and polynomials, try using Pari. If you are a LISP user or want to do vector operations or statistics, consider using the LISP-STAT package.

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