OK, Well - I'm getting only so so far with this... I seem to have a reasonable HWPREDICT value, but I do have some problems with my CDEF for confidence bands - perhaps I'm being stupid with RPN... It is a bit messy, but I'm just trying to get something to work... here is my graph:

**Code:**

/usr/bin/rrdtool graph - \

--imgformat=PNG \

--start=-86400 \

--end=-300 \

--title="Holt-Winters Testing - Giles" \

--base=1000 \

--height=350 \

--width=700 \

--alt-autoscale-max \

--lower-limit=0 \

--vertical-label="bits per second" \

--slope-mode \

DEF:a="/var/www/sites/stats/web/rra/bst_snmp_oid_2577.rrd":snmp_oid:AVERAGE \

DEF:b="/var/www/sites/stats/web/rra/bst_snmp_oid_2578.rrd":snmp_oid:AVERAGE \

DEF:c="/var/www/sites/stats/web/rra/bst_snmp_oid_2577.rrd":snmp_oid:HWPREDICT \

DEF:d="/var/www/sites/stats/web/rra/bst_snmp_oid_2577.rrd":snmp_oid:DEVPREDICT \

CDEF:cdefa=a,8,* \

CDEF:cdefe=b,8,* \

CDEF:cdefi=d,2,*,c,+,8,* \

CDEF:cdefj=d,-2,*,c,+,8,* \

CDEF:cdefbb=d,8,* \

CDEF:cdefbc=c,8,* \

AREA:cdefa#00CF00:"Inbound" \

GPRINT:cdefa:LAST:" Current\:%8.2lf %s" \

GPRINT:cdefa:AVERAGE:"Average\:%8.2lf %s" \

GPRINT:cdefa:MAX:"Maximum\:%8.2lf %s\n" \

LINE1:cdefe#4444FF:"Outbound" \

GPRINT:cdefe:LAST:" Current\:%8.2lf %s" \

GPRINT:cdefe:AVERAGE:"Average\:%8.2lf %s" \

GPRINT:cdefe:MAX:"Maximum\:%8.2lf %s\n" \

LINE1:cdefi#FF0000:"Confidence Bands (Testing)\n" \

LINE1:cdefj#FF0000:"" \

LINE1:d:"" \

LINE1:cdefbb#000000:"Predicted Value" \

GPRINT:cdefbc:HWPREDICT:" %8.2lf %s\n" \

GPRINT:cdefbb:DEVPREDICT:"Deviation\:%8.2lf %s"

My SNMP values are in bytes and I want bits.

My understanding is that if I take HWPREDICT, I can get two confidence bands by plotting HWPREDICT + (2*DEVPREDICT) and HWPREDICT - (2*DEVPREDICT)

The problem I have with the above graph is that the Confidence bands do not appear to be equidistant from the HWPREDICT graph, and in some places the confidence bands actually cross the HWPREDICT graph.

I've tried the following RPN notations for CDEFs to calculate the confidence bands - (CDS = Current Datasource))

CDS,d,2,*,+,8,* & CDS,d,-2,*,+,8,*

CDS,8,*,d,16,*,+ & CDS,8,*,d,-16,*,+

am I doing something (RPN) stupid, or is there a deeper problem here?