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/* This program was used to create the figure in the accompanying memo.  
   You can find a copy of this program in ~amr/plplot/examples/tutor.c */

/* This program is intended to be used as a template for creating simple 
   two-dimensional plotting programs which use the Plplot plotting library.
   The program was written with an emphasis on trying to clearly illustrate 
   how to use the Plplot library functions.  It is probably not an example 
   of good C programming style. */

/* This program reads data for M lines with N points each from an
   input data file and plots them on the same graph using different
   symbols.  It draws axes with labels and places a title at the top
   of the figure.  A legend is drawn to the right of the figure.
   The input data file must have the following format:

   M          N
   x[1]     y[1][1]     y[1][2]     .     .     .     y[1][M]
   x[2]     y[2][1]     y[2][2]     .     .     .     y[2][M]
   x[3]     y[3][1]     y[3][2]     .     .     .     y[3][M]
    .          .           .        .     .     .        .
    .          .           .        .     .     .        .
    .          .           .        .     .     .        .
   x[N]     y[N][1]     y[N][2]     .     .     .     y[N][M]

   (The first line contains the integer values M and N.  The succeeding
   N lines contain the x-coordinate and the corresponding y-coordinates
   of each of the M lines.) */

#include <stdio.h>
#include <string.h>
#include <math.h>

/* You can select a different set of symbols to use when plotting the
   lines by changing the value of OFFSET. */
#define OFFSET  2

  /* ==============  Begin variable definition section. ============= */

   /* i, j, and k  are counting variables used in loops and such. M is 
      the number of lines to be plotted and N is the number of 
      sample points for each line. */
   int i, j, k, M, N, leglen;

   /* x is a pointer to an array containing the N x-coordinate values.
      y points to an array of M pointers each of which points to an
      array containing the N y-coordinate values for that line. */
   float *x, **y;

   /* Define storage for the min and max values of the data. */
   float xmin, xmax, ymin, ymax, xdiff, ydiff;

   /* Define storage for the filename and define the input file pointer. */
   char filename[80], string[80], tmpstr[80];
   FILE *datafile;

   /* Here are the character strings that appear in the plot legend. */
   static char *legend[] = {
      NULL };     /* Make sure last element is NULL */
  /* ==============  Read in data from input file. ============= */

    /* First prompt the user for the input data file name */
    printf("Enter input data file name. ");
    /* and open the file. */
    datafile = fopen(filename,"r");
    if(datafile == NULL)  /* error opening input file */
        error("Error opening input file.");

    /* Read in values of M and N */
    k = fscanf(datafile,"%d %d",&M,&N);
    if(k != 2)   /* something's wrong */
        error("Error while reading data file.");

    /* Allocate memory for all the arrays. */
    x = (float *)malloc(N*sizeof(float));
    if(x == NULL) error("Out of memory!");
    y = (float **)malloc(M*sizeof(float *));
    if(y == NULL) error("Out of memory!");
    for(i=0;i<M;i++) {
        y[i] = (float *)malloc(N*sizeof(float));
        if(y[i] == NULL) error("Out of memory!");
    /* Now read in all the data. */
    for(i=0;i<N;i++)   { /* N points */
        k = fscanf(datafile,"%f",&x[i]);
        if(k != 1) error("Error while reading data file.");
        for(j=0;j<M;j++) { /* M lines */
            k = fscanf(datafile,"%f",&y[j][i]);
            if(k != 1) error("Error while reading data file.");
  /* ==============  Graph the data. ============= */

    /* Set graph to portrait orientation. (Default is landscape.) */
    /* (Portrait is usually desired for inclusion in TeX documents.) */

    /* Prompt user for the output device or file type. */
    /* You may want to use plbeg() instead, if you always use the
       same graphics file type. (see the Plplot manual) I only want
       one large subpage here so I use the arguments (1,1). */
    /* We must call pladv() to advance to the first (and only)
       subpage.  You might want to use plenv() instead of the
       pladv(), plvpor(), plwind() sequence. */

    /* Set up the viewport.  This is the window into which the data
       is plotted.  The size of the window can be set with a call
       to plvpor(), which sets the size in terms of normalized
       subpage coordinates.  I want to plot the lines on the upper
       half of the page and I want to leave room to the right of
       the figure for labelling the lines. We must also leave room
       for the title and labels with plvpor().  Normally a call to 
       plvsta() can be used instead. */

    /* We now need to define the size of the window in user
       coordinates.  To do this, we first need to determine the
       range of the data values. */
    xmin = xmax = x[0];
    ymin = ymax = y[0][0];
    for(i=0;i<N;i++) {
        if(x[i] < xmin) xmin=x[i];
        if(x[i] > xmax) xmax=x[i];
        for(j=0;j<M;j++) {
            if(y[j][i] < ymin) ymin=y[j][i];
            if(y[j][i] > ymax) ymax=y[j][i];
    /* Now set the size of the window. Leave a small border 
       around the data. */
    xdiff = (xmax-xmin)/20.;
    ydiff = (ymax-ymin)/20.;
    /* Call plbox() to draw the axes (see the PLPLOT manual for
       information about the option strings.) */

    /* Label the axes and title the graph. */
    /* The string "#gm" plots the Greek letter mu, all the Greek
       letters are available, see the Plplot manual. */
    pllab("Time (weeks)","Height (#gmparsecs)","Specimen Growth Rate");

    /* Plot the data. */
    /* plpoin() draws a symbol at each point. */
    /* plline() connects all the points. */
    for(i=0;i<M;i++) {

    /* Draw legend to the right of the chart. */
    /* Things get a little messy here.  You may want to remove this
       section if you don't want a legend drawn. */
    /* First find length of longest string. */
    leglen = 0;
    for(i=0;i<M;i++) {
        if(legend[i] == NULL) break;
        j = strlen(legend[i]);
        if(j > leglen) leglen = j;
    /* Now build the string.  The string consists of an element from
       the legend string array, padded with spaces, followed by one
       of the symbols used in plpoin above. */
    for(i=0;i<M;i++) {
        if(legend[i] == NULL) break;
        j = strlen(string);
        if(j < leglen) {  /* pad string with spaces */
                string[k] = ' ';
            string[k] = NULL;
        /* pad an extra space */
        strcat(string," ");
        j = strlen(string);
        /* insert the ASCII value of the symbol plotted with plpoin() */
        string[j] = i+OFFSET;
        string[j+1] = NULL;
        /* plot the string */

    /*  Tell plplot we are done with this page. */
    pleop();    /* end page */

    /* Don't forget to call PLEND to finish off! */

int error(str)
char *str;

These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Marcel Waldvogel and Netfuture.ch.