• Graphing tools
• High Level Languages
• Simple programming
• Publication tools
• Web tools

We need to plot data. We'll use a package called gnuplot (pronounced "new-plot").

• Open terminal window
• Type gnuplot<return>
• plot
• set xrange, yrange
• set log, nolog, set log x[y], set nolog x[y]
• set grid, nogrid, key, nokey
• set xlabel, ylabel, title
• printing - set term post, set output 'filename.ps', plot, set output, set term x11

Plot the following data by first copying to a file, and then using gnuplot to read and plot from that file.

 1   -13.600 
 2   -3.400 
 3   -1.511 
 4   -0.850 
 5   -0.544 
 6   -0.378 
 7   -0.278 
 8   -0.213 
 9   -0.168 
10   -0.136 

• Computers speak machine language, thousands of 1s and 0s.
• We speak english (or some such human language).
• We need some way to get the computer to understand and carry out our instructions.

• We right down our instructions in a highly structured way called a high level language.
•  The computer uses an interpreter to take the high level language and translate it into machine language.

The interpreter that translates the source code into machine code is called the compiler.

High Level Languages

• FORTRAN (FORTRAN 77, FORTRAN 90)
• C, C++
• BASIC
• PASCAL
• JAVA
• etc . . .

• Skeleton Code
• Example 1
• Example 2
• Intrinsic Functions
• Compiling & Executing Code
• Exercise #2

• program name
• variable declarations
• initialize variables
• calculations
• input/output
• end program

    pi = 2.0 * asin(1.0)
    print *, 'pi = ',pi

    end program picalc

//This is a program that calculates the value of pi
//using the intrinsic funtion asin. The value of pi
//is written to the screen after it is calculated.

#include < iostream>    // this is needed for output to screen
#include < math.h>         // this is needed for the asin function

int main(){

double pi;

pi = 2.0 * asin(1.0);
cout << "pi = " << pi << endl;

}

    pi = 2.0 * asin(1.0)

    open(unit=10,file='data.dat')

    do degs = 0.0, 180.0, 10.0
        rads = degs * pi / 180.0
        write(10,*) degs, rads
    enddo

    close(10)

    end program deg2rad

// This program calculates the radian equivalent of
// angles in degrees, for every 10 degrees from 0 to 180.

#include < iostream>
#include < math.h>

int main(){

double pi, rads;
pi = 2.0 * asin(1.0);

for(double degs = 0.; degs <= 180.; degs += 10.;){
  rads = degs * pi / 180.;
  cout << degs << "   " << rads << endl;
  }

}

• x + y, x - y
• x * y, x / y
• sin(x), asin(x)
• cos(x), acos(x)
• tan(x), atan(x)
• log(x), exp(x)
• log10(x)
• x**y (x^y)

• Edit source code in editor
• save code to file source_file.f or source_file.cc
• compile code with: f77 -o executable_name source_file.f
  compile code with: g++ -o executable_name source_file.cc
  
• execute code with executable_name

• Write a program to output y = sin(x) from 0 to 180^o to a file called sinewave.dat.
• Remember that trigonometric intrinsics take arguments in radians, not degrees.
• Plot the data in gnuplot using the command plot 'sinewave.dat'.
• Plot the data on the same graph with the analytic function sin(x) with something like plot 'sinewave.dat', sin(x) (but not exactly!).
• Set the title and axis labels, and save a copy of the graph to a file called sinewave.ps.

• LaTeX is much like a high level computer language.
• You provide a source file describing a document you wish to have created (typeset).
• LaTeX is much like the compiler, and turns the source into a finished document.

• Again, HTML is a language. You descibe a web page with a source file, someone's browser builds the web page from it.