New VDEF functions for least squares slope, intercept & correlation for simple foreca...

[rrdtool.git] / src / rrd_graph.c

diff --git a/src/rrd_graph.c b/src/rrd_graph.c
index 2a13cb5..3ce3959 100644 (file)
--- a/src/rrd_graph.c
+++ b/src/rrd_graph.c
@@ -3406,6 +3406,9 @@ char *str;
     else if    (!strcmp("TOTAL",  func)) gdes->vf.op = VDEF_TOTAL;
     else if    (!strcmp("FIRST",  func)) gdes->vf.op = VDEF_FIRST;
     else if    (!strcmp("LAST",   func)) gdes->vf.op = VDEF_LAST;
+    else if     (!strcmp("LSLSLOPE", func)) gdes->vf.op = VDEF_LSLSLOPE;
+    else if     (!strcmp("LSLINT",   func)) gdes->vf.op = VDEF_LSLINT;
+    else if     (!strcmp("LSLCORREL",func)) gdes->vf.op = VDEF_LSLCORREL;
     else {
        rrd_set_error("Unknown function '%s' in VDEF '%s'\n"
            ,func
@@ -3441,6 +3444,9 @@ char *str;
        case VDEF_TOTAL:
        case VDEF_FIRST:
        case VDEF_LAST:
+       case VDEF_LSLSLOPE:
+       case VDEF_LSLINT:
+       case VDEF_LSLCORREL:
            if (isnan(param)) {
                gdes->vf.param = DNAN;
                gdes->vf.val   = DNAN;
@@ -3599,6 +3605,48 @@ printf("DEBUG: %3li:%10.2f %c\n",step,array[step],step==field?'*':' ');
                dst->vf.when = src->start + (step+1)*src->step;
            }
            break;
+       case VDEF_LSLSLOPE:
+       case VDEF_LSLINT:
+       case VDEF_LSLCORREL:{
+           /* Bestfit line by linear least squares method */ 
+
+           int cnt=0;
+           double SUMx, SUMy, SUMxy, SUMxx, SUMyy, slope, y_intercept, correl ;
+           SUMx = 0; SUMy = 0; SUMxy = 0; SUMxx = 0; SUMyy = 0;
+
+           for (step=0;step<steps;step++) {
+               if (finite(data[step*src->ds_cnt])) {
+                   cnt++;
+                   SUMx  += step;
+                   SUMxx += step * step;
+                   SUMxy += step * data[step*src->ds_cnt];
+                   SUMy  += data[step*src->ds_cnt];
+                   SUMyy  += data[step*src->ds_cnt]*data[step*src->ds_cnt];
+               };
+           }
+
+           slope = ( SUMx*SUMy - cnt*SUMxy ) / ( SUMx*SUMx - cnt*SUMxx );
+           y_intercept = ( SUMy - slope*SUMx ) / cnt;
+           correl = (SUMxy - (SUMx*SUMy)/cnt) / sqrt((SUMxx - (SUMx*SUMx)/cnt)*(SUMyy - (SUMy*SUMy)/cnt));
+
+           if (cnt) {
+                   if (dst->vf.op == VDEF_LSLSLOPE) {
+                       dst->vf.val  = slope;
+                       dst->vf.when = cnt*src->step;
+                   } else if (dst->vf.op == VDEF_LSLINT)  {
+                       dst->vf.val = y_intercept;
+                       dst->vf.when = cnt*src->step;
+                   } else if (dst->vf.op == VDEF_LSLCORREL)  {
+                       dst->vf.val = correl;
+                       dst->vf.when = cnt*src->step;
+                   };
+               
+           } else {
+               dst->vf.val  = DNAN;
+               dst->vf.when = 0;
+           }
+           }
+           break;
     }
     return 0;
 }