+static double
+calculate_iqr (void)
+{
+ double q1 = SYSMIS;
+ double q3 = SYSMIS;
+ int i;
+
+ for (i = 0; i < n_percentiles; i++)
+ {
+ if (fabs (0.25 - percentiles[i].p) < DBL_EPSILON)
+ q1 = percentiles[i].value;
+ else if (fabs (0.75 - percentiles[i].p) < DBL_EPSILON)
+ q3 = percentiles[i].value;
+ }
+
+ return q1 == SYSMIS || q3 == SYSMIS ? SYSMIS : q3 - q1;
+}