rrd_graph_rpn: add a MEDIAN operator. -- Aaron Gallagher <_@habnab.it>

[rrdtool.git] / src / rrd_rpncalc.c

diff --git a/src/rrd_rpncalc.c b/src/rrd_rpncalc.c
index 8dd2240..0677b30 100644 (file)
--- a/src/rrd_rpncalc.c
+++ b/src/rrd_rpncalc.c
@@ -33,8 +33,8 @@ short rpn_compact(
     while (rpnp[*count].op != OP_END)
         (*count)++;
     if (++(*count) > DS_CDEF_MAX_RPN_NODES) {
-        rrd_set_error("Maximum %d RPN nodes permitted",
-                      DS_CDEF_MAX_RPN_NODES);
+        rrd_set_error("Maximum %d RPN nodes permitted. Got %d RPN nodes at present.",
+                      DS_CDEF_MAX_RPN_NODES-1,(*count)-1);
         return -1;
     }
 
@@ -236,9 +236,11 @@ void parseCDEF_DS(
      * occur too often. */
     for (i = 0; rpnp[i].op != OP_END; i++) {
         if (rpnp[i].op == OP_TIME || rpnp[i].op == OP_LTIME ||
-            rpnp[i].op == OP_PREV || rpnp[i].op == OP_COUNT) {
+            rpnp[i].op == OP_PREV || rpnp[i].op == OP_COUNT ||
+            rpnp[i].op == OP_TREND || rpnp[i].op == OP_TRENDNAN ||
+            rpnp[i].op == OP_PREDICT || rpnp[i].op ==  OP_PREDICTSIGMA ) {
             rrd_set_error
-                ("operators time, ltime, prev and count not supported with DS COMPUTE");
+                ("operators TIME, LTIME, PREV COUNT TREND TRENDNAN PREDICT PREDICTSIGMA are not supported with DS COMPUTE");
             free(rpnp);
             return;
         }
@@ -385,6 +387,7 @@ rpnp_t   *rpn_parse(
             match_op(OP_AVG, AVG)
             match_op(OP_ABS, ABS)
             match_op(OP_ADDNAN, ADDNAN)
+            match_op(OP_MEDIAN, MEDIAN)
 #undef match_op
             else if ((sscanf(expr, DEF_NAM_FMT "%n", vname, &pos) == 1)
                      && ((rpnp[steps].ptr = (*lookup) (key_hash, vname)) !=
@@ -934,6 +937,51 @@ short rpn_calc(
             stackunderflow(0);
             rpnstack->s[stptr] = fabs(rpnstack->s[stptr]);
             break;
+        case OP_MEDIAN:
+            stackunderflow(0);
+            {
+                int elements = (int) rpnstack->s[stptr--];
+                int final_elements = elements;
+                double *element_ptr = rpnstack->s + stptr - elements + 1;
+                double *goodvals = element_ptr;
+                double *badvals = element_ptr + elements - 1;
+
+                stackunderflow(elements - 1);
+
+                /* move values to consolidate the non-NANs for sorting, keeping
+                 * track of how many NANs we encounter. */
+                while (goodvals < badvals) {
+                    if (isnan(*goodvals)) {
+                        *goodvals = *badvals--;
+                        --final_elements;
+                    } else {
+                        ++goodvals;
+                    }
+                }
+
+                stptr -= elements;
+                if (!final_elements) {
+                    /* no non-NAN elements; push NAN */
+                    rpnstack->s[++stptr] = DNAN;
+                } else {                   
+                    /* when goodvals and badvals meet, they might have met on a
+                     * NAN, which wouldn't decrease final_elements. so, check
+                     * that now. */
+                    if (isnan(*goodvals)) --final_elements;
+                    /* and finally, take the median of the remaining non-NAN
+                     * elements. */
+                    qsort(element_ptr, final_elements, sizeof(double),
+                          rpn_compare_double);
+                    if (final_elements % 2 == 1){
+                       rpnstack->s[++stptr] = element_ptr[ final_elements / 2 ];
+                    }
+                    else {
+                       rpnstack->s[++stptr] = 0.5 * ( element_ptr[ final_elements / 2 ] + element_ptr[ final_elements / 2 - 1 ] );
+                    }
+                }
+            }
+            break;
+       
         case OP_END:
             break;
         }