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<title>GNU Scientific Library – Reference Manual: Sorting Examples</title>
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<p>
Next: <a href="Sorting-References-and-Further-Reading.html#Sorting-References-and-Further-Reading" accesskey="n" rel="next">Sorting References and Further Reading</a>, Previous: <a href="Computing-the-rank.html#Computing-the-rank" accesskey="p" rel="previous">Computing the rank</a>, Up: <a href="Sorting.html#Sorting" accesskey="u" rel="up">Sorting</a> [<a href="Function-Index.html#Function-Index" title="Index" rel="index">Index</a>]</p>
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<hr>
<a name="Examples-6"></a>
<h3 class="section">12.5 Examples</h3>
<p>The following example shows how to use the permutation <var>p</var> to print
the elements of the vector <var>v</var> in ascending order,
</p>
<div class="example">
<pre class="example">gsl_sort_vector_index (p, v);
for (i = 0; i < v->size; i++)
{
double vpi = gsl_vector_get (v, p->data[i]);
printf ("order = %d, value = %g\n", i, vpi);
}
</pre></div>
<p>The next example uses the function <code>gsl_sort_smallest</code> to select
the 5 smallest numbers from 100000 uniform random variates stored in an
array,
</p>
<div class="example">
<pre class="verbatim">#include <gsl/gsl_rng.h>
#include <gsl/gsl_sort_double.h>
int
main (void)
{
const gsl_rng_type * T;
gsl_rng * r;
size_t i, k = 5, N = 100000;
double * x = malloc (N * sizeof(double));
double * small = malloc (k * sizeof(double));
gsl_rng_env_setup();
T = gsl_rng_default;
r = gsl_rng_alloc (T);
for (i = 0; i < N; i++)
{
x[i] = gsl_rng_uniform(r);
}
gsl_sort_smallest (small, k, x, 1, N);
printf ("%d smallest values from %d\n", k, N);
for (i = 0; i < k; i++)
{
printf ("%d: %.18f\n", i, small[i]);
}
free (x);
free (small);
gsl_rng_free (r);
return 0;
}
</pre></div>
<p>The output lists the 5 smallest values, in ascending order,
</p>
<div class="example">
<pre class="example">$ ./a.out
</pre><pre class="verbatim">5 smallest values from 100000
0: 0.000003489200025797
1: 0.000008199829608202
2: 0.000008953968062997
3: 0.000010712770745158
4: 0.000033531803637743
</pre></div>
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