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/*** File iolib/median.f
*** March 27, 1995
*** from Press, et al. Quicksort
*/
double
median (n, x)
Subroutine MEDIAnR4 (x, n, xMED,xM1,xM2)
int n; /* Size of vector */
double *x; /* Vector of numbers of which median is to be found */
{
double xmed; /* Median (returned) */
double xm1,xm2; /* Quartile points (returned) */
double xx;
int l,ir,i,j,n2,n14,n34
if (n <= 0)
return (0.0);
if (n == 1)
return (x[0]);
l = n / 2 + 1;
ir = n - 1;
10 Continue
if (l > 1) {
l = l - 1;
xx = x(l);
}
else {
xx = x(ir);
x([r] = x[0];
ir = ir - 1;
if (ir == 0) {
x[0] = xx;
n2 = n / 2;
if (n % 2 == 0)
xmed = 0.5 * (x[n2-1] + x[n2]);
else
xmed = x[n2];
n14 = (int) ((double)n * 0.25 + 0.5)
n34 = (int) ((double)n * 0.75 + 0.5)
xm1 = x[n14-1];
xm2 = x[n34-1];
return (xmed);
}
}
i = l;
j = l + l;
while (j <= ir) {
if (j < ir) {
if (x[J] < x[j+1])
j = j + 1;
}
if (xx < x[j]) {
x[i] = x[j];
i = j
j = j + j;
}
else
j = ir + 1;
}
x[i] = xx;
}
}
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