From c6bbce5f7558012214b35a712b4953f1121f849d Mon Sep 17 00:00:00 2001
From: oetiker <oetiker@a5681a0c-68f1-0310-ab6d-d61299d08faa>
Date: Sat, 8 Sep 2007 05:23:23 +0000
Subject: [PATCH] added STDEV aggregation function for VDEF. -- Patrick J
 Cherry patrick bytemark.co.uk

git-svn-id: svn://svn.oetiker.ch/rrdtool/trunk/program@1201 a5681a0c-68f1-0310-ab6d-d61299d08faa
---
 CONTRIBUTORS         |  1 +
 doc/rrdgraph_rpn.pod |  6 ++++++
 src/rrd_graph.c      | 17 ++++++++++++++++-
 src/rrd_graph.h      |  1 +
 4 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/CONTRIBUTORS b/CONTRIBUTORS
index 54a6a6c..a44edcb 100644
--- a/CONTRIBUTORS
+++ b/CONTRIBUTORS
@@ -38,6 +38,7 @@ Mike Mitchell <mcm with unx.sas.com>
 Mike Slifcak <slif with bellsouth.net> many rrdtool-1.1.x fixes
 Oleg Cherevko <olwi with icyb.kiev.ua>
 Otmar Lendl <O.Lendl with Austria.EU.net> (lots of bugfixes)
+Patrick Cherry <patrick with bytemark.co.uk>
 Paul Joslin <Paul.Joslin with sdrc.com>
 Peter Speck <speck with vitality.dk> eps/svg/pdf file format code in rrdtool-1.x
 Peter Stamfest <peter with stamfest.at> initial multi-thread support
diff --git a/doc/rrdgraph_rpn.pod b/doc/rrdgraph_rpn.pod
index cf62c08..3718349 100644
--- a/doc/rrdgraph_rpn.pod
+++ b/doc/rrdgraph_rpn.pod
@@ -257,6 +257,12 @@ the first occurrence of that value in the time component.
 
 Example: C<VDEF:avg=mydata,AVERAGE>
 
+=item STDEV
+
+Returns the standard deviation of the values.
+
+Example: C<VDEF:stdev=mydata,STDEV>
+
 =item LAST, FIRST
 
 Return the last/first value including its time.  The time for
diff --git a/src/rrd_graph.c b/src/rrd_graph.c
index 348a5a5..b624171 100644
--- a/src/rrd_graph.c
+++ b/src/rrd_graph.c
@@ -4285,6 +4285,8 @@ int vdef_parse(
         gdes->vf.op = VDEF_MAXIMUM;
     else if (!strcmp("AVERAGE", func))
         gdes->vf.op = VDEF_AVERAGE;
+    else if (!strcmp("STDEV", func))
+        gdes->vf.op = VDEF_STDEV;
     else if (!strcmp("MINIMUM", func))
         gdes->vf.op = VDEF_MINIMUM;
     else if (!strcmp("TOTAL", func))
@@ -4324,6 +4326,7 @@ int vdef_parse(
         break;
     case VDEF_MAXIMUM:
     case VDEF_AVERAGE:
+    case VDEF_STDEV:
     case VDEF_MINIMUM:
     case VDEF_TOTAL:
     case VDEF_FIRST:
@@ -4412,9 +4415,11 @@ int vdef_calc(
         }
         break;
     case VDEF_TOTAL:
+    case VDEF_STDEV:
     case VDEF_AVERAGE:{
         int       cnt = 0;
         double    sum = 0.0;
+        double    average = 0.0;
 
         for (step = 0; step < steps; step++) {
             if (finite(data[step * src->ds_cnt])) {
@@ -4426,9 +4431,19 @@ int vdef_calc(
             if (dst->vf.op == VDEF_TOTAL) {
                 dst->vf.val = sum * src->step;
                 dst->vf.when = 0;   /* no time component */
-            } else {
+            } else if (dst->vf.op == VDEF_AVERAGE){
                 dst->vf.val = sum / cnt;
                 dst->vf.when = 0;   /* no time component */
+            } else {
+                average = sum / cnt;
+                sum = 0.0;
+                for (step=0;step<steps;step++) {
+                    if (finite(data[step*src->ds_cnt])) {
+                        sum += pow((data[step*src->ds_cnt] - average),2.0);
+                    };
+                }
+                dst->vf.val  = pow(sum / cnt,0.5);
+                dst->vf.when = 0; /* no time component */
             };
         } else {
             dst->vf.val = DNAN;
diff --git a/src/rrd_graph.h b/src/rrd_graph.h
index 00ab15b..dd13237 100644
--- a/src/rrd_graph.h
+++ b/src/rrd_graph.h
@@ -54,6 +54,7 @@ enum vdef_op_en {
     VDEF_MAXIMUM = 0    /* like the MAX in (G)PRINT */
         , VDEF_MINIMUM  /* like the MIN in (G)PRINT */
         , VDEF_AVERAGE  /* like the AVERAGE in (G)PRINT */
+        , VDEF_STDEV    /* the standard deviation */
         , VDEF_PERCENT  /* Nth percentile */
         , VDEF_TOTAL    /* average multiplied by time */
         , VDEF_FIRST    /* first non-unknown value and time */
-- 
2.30.2