New to rrdtool. I want to look at the efforts needed to create a line of best fit with RRD schedules so that we can identify long-term trends, that is, value increases over time. I recently used the Perl Statistics :: LineFit module to help establish regression trends. Maybe RRD itself has a tool that makes linear regression easier to do?
I looked at the documentation of PREDICT, PREDICTSIGMA and tried to make the settings below, but this gives me an error below. Any suggestions please.
rrdtool graph image.png --imgformat=PNG \
--start=-7days --end=+3days --width=1000 --height=200 --alt-autoscale-max \ DEF:value=value.rrd:value:AVERAGE:start=-14days \
LINE1:value#ff0000:value \
CDEF:predict=86400,-7,1800,value,PREDICT \
CDEF:sigma=86400,-7,1800,value,PREDICTSIGMA \
CDEF:upper=predict,sigma,3,*,+ \
CDEF:lower=predict,sigma,3,*,- \
LINE1:predict#00ff00:prediction \
LINE1:upper#0000ff:upper\ certainty\ limit \
LINE1:lower#0000ff:lower\ certainty\ limit \ CDEF:exceeds=value,UN,0,value,lower,upper,LIMIT,UN,IF \
TICK:exceeds#aa000080:1
ERROR
[ERROR: invalid rpn expression in: 86400, -7.1800, value, PREDICT]