![[tokkee]](http://tokkee.org/images/avatar.png){kind=avatar}
diff --git a/doc/rrdgraph_rpn.txt b/doc/rrdgraph_rpn.txt
index 6ca5af3fcd6f5f6bbe083fa063a7d67a089b087f..327dc0d6629813faf8ab0f71d0e026160f6f20a6 100644 (file)
--- a/doc/rrdgraph_rpn.txt
+++ b/doc/rrdgraph_rpn.txt
_\bR_\bP_\bN _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn:=_\bv_\bn_\ba_\bm_\be|_\bo_\bp_\be_\br_\ba_\bt_\bo_\br|_\bv_\ba_\bl_\bu_\be[,_\bR_\bP_\bN _\be_\bx_\bp_\br_\be_\bs_\bs_\bi_\bo_\bn]
D\bDE\bES\bSC\bCR\bRI\bIP\bPT\bTI\bIO\bON\bN
- If you have ever used a traditional HP calculator you already know R\bRP\bPN\bN.
- The idea behind R\bRP\bPN\bN is that you have a stack and push your data onto
- this stack. Whenever you execute an operation, it takes as many ele-
- ments from the stack as needed. Pushing is done implicitly, so whenever
- you specify a number or a variable, it gets pushed onto the stack auto-
- matically.
+ If you have ever used a traditional HP calculator you already know R\bRP\bPN\bN
+ (Reverse Polish Notation). The idea behind R\bRP\bPN\bN is that you have a
+ stack and push your data onto this stack. Whenever you execute an oper-
+ ation, it takes as many elements from the stack as needed. Pushing is
+ done implicitly, so whenever you specify a number or a variable, it
+ gets pushed onto the stack automatically.
At the end of the calculation there should be one and only one value
left on the stack. This is the outcome of the function and this is
The TRENDNAN operation ignores all NAN-values in a sliding window
and computes the average of the remaining values.
+ P\bPR\bRE\bED\bDI\bIC\bCT\bT,\b, P\bPR\bRE\bED\bDI\bIC\bCT\bTS\bSI\bIG\bGM\bMA\bA
+
+ Create a "sliding window" average/sigma of another data series,
+ that also shifts the data series by given amounts of of time as
+ well
+
+ Usage - explicit stating shifts: CDEF:predict=<shift n>,...,<shift
+ 1>,n,<window>,x,PREDICT CDEF:sigma=<shift n>,...,<shift 1>,n,<win-
+ dow>,x,PREDICTSIGMA
+
+ Usage - shifts defined as a base shift and a number of time this is
+ applied CDEF:predict=<shift multiplier>,-n,<window>,x,PREDICT
+ CDEF:sigma=<shift multiplier>,-n,<window>,x,PREDICTSIGMA
+
+ Example: CDEF:predict=172800,86400,2,1800,x,PREDICT
+
+ This will create a half-hour (1800 second) sliding window aver-
+ age/sigma of x, that average is essentially computed as shown here:
+
+ +---!---!---!---!---!---!---!---!---!---!---!---!---!---!---!---!---!--->
+ now
+ shift 1 t0
+ <----------------------->
+ window
+ <--------------->
+ shift 2
+ <----------------------------------------------->
+ window
+ <--------------->
+ shift 1 t1
+ <----------------------->
+ window
+ <--------------->
+ shift 2
+ <----------------------------------------------->
+ window
+ <--------------->
+
+ Value at sample (t0) will be the average between (t0-shift1-window) and (t0-shift1)
+ and between (t0-shift2-window) and (t0-shift2)
+ Value at sample (t1) will be the average between (t1-shift1-window) and (t1-shift1)
+ and between (t1-shift2-window) and (t1-shift2)
+
+ The function is by design NAN-safe. This also allows for extrapo-
+ lation into the future (say a few days) - you may need to define
+ the data series whit the optional start= parameter, so that the
+ source data series has enough data to provide prediction also at
+ the beginning of a graph...
+
+ Here an example, that will create a 10 day graph that also shows
+ the prediction 3 days into the future with its uncertainty value
+ (as defined by avg+-4*sigma) This also shows if the prediction is
+ exceeded at a certain point.
+
+ 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
+
+ Note: Experience has shown that a factor between 3 and 5 to scale
+ sigma is a good discriminator to detect abnormal behaviour. This
+ obviously depends also on the type of data and how "noisy" the data
+ series is.
+
+ This prediction can only be used for short term extrapolations -
+ say a few days into the future-
+
Special values
U\bUN\bNK\bKN\bN
Example: "VDEF:total=mydata,TOTAL"
- PERCENT
+ PERCENT, PERCENTNAN
This should follow a D\bDE\bEF\bF or C\bCD\bDE\bEF\bF _\bv_\bn_\ba_\bm_\be. The _\bv_\bn_\ba_\bm_\be is popped,
another number is popped which is a certain percentage (0..100).
The data set is then sorted and the value returned is chosen such
that _\bp_\be_\br_\bc_\be_\bn_\bt_\ba_\bg_\be percent of the values is lower or equal than the
- result. _\bU_\bn_\bk_\bn_\bo_\bw_\bn values are considered lower than any finite number
- for this purpose so if this operator returns an _\bu_\bn_\bk_\bn_\bo_\bw_\bn you have
- quite a lot of them in your data. I\bIn\bnf\bfinite numbers are lesser, or
- more, than the finite numbers and are always more than the _\bU_\bn_\bk_\bn_\bo_\bw_\bn
- numbers. (NaN < -INF < finite values < INF)
+ result. For PERCENTNAN _\bU_\bn_\bk_\bn_\bo_\bw_\bn values are ignored, but for PERCENT
+ _\bU_\bn_\bk_\bn_\bo_\bw_\bn values are considered lower than any finite number for this
+ purpose so if this operator returns an _\bu_\bn_\bk_\bn_\bo_\bw_\bn you have quite a lot
+ of them in your data. I\bIn\bnf\bfinite numbers are lesser, or more, than
+ the finite numbers and are always more than the _\bU_\bn_\bk_\bn_\bo_\bw_\bn numbers.
+ (NaN < -INF < finite values < INF)
Example: "VDEF:perc95=mydata,95,PERCENT"
+ "VDEF:percnan95=mydata,95,PERCENTNAN"
LSLSLOPE, LSLINT, LSLCORREL
Return the parameters for a L\bLeast S\bSquares L\bLine _\b(_\by _\b= _\bm_\bx _\b+_\bb_\b) which
A\bAU\bUT\bTH\bHO\bOR\bR
Program by Tobias Oetiker <tobi@oetiker.ch>
- This manual page by Alex van den Bogaerdt <alex@ergens.op.het.net>
+ This manual page by Alex van den Bogaerdt <alex@vandenbogaerdt.nl> with
+ corrections and/or additions by several people
-1.3.1 2008-03-15 RRDGRAPH_RPN(1)
+1.3.99909060808 2009-02-21 RRDGRAPH_RPN(1)