RRDGRAPH_DATA(1)                    rrdtool                   RRDGRAPH_DATA(1)



NNAAMMEE
       rrdgraph_data - preparing data for graphing in rrdtool graph

SSYYNNOOPPSSIISS
       DDEEFF::_<_v_n_a_m_e_>=_<_r_r_d_f_i_l_e_>:_<_d_s_-_n_a_m_e_>:_<_C_F_>[:step=_<_s_t_e_p_>][:start=_<_t_i_m_e_>][:end=_<_t_i_m_e_>][:reduce=_<_CC_FF_>]

       VVDDEEFF:_v_n_a_m_e=_R_P_N _e_x_p_r_e_s_s_i_o_n

       CCDDEEFF:_v_n_a_m_e=_R_P_N _e_x_p_r_e_s_s_i_o_n

DDEESSCCRRIIPPTTIIOONN
       These three instructions extract data values out of the RRRRDD files,
       optionally altering them (think, for example, of a bytes to bits
       conversion). If so desired, you can also define variables containing
       useful information such as maximum, minimum etcetera. Two of the
       instructions use a language called RRPPNN which is described in its own
       manual page.

       Variable names (_v_n_a_m_e) must be made up strings of the following
       characters "A-Z, a-z, 0-9, -,_" and a maximum length of 255 characters.

       When picking variable names, make sure you do not choose a name that is
       already taken by an RPN operator. A safe bet it to use lowercase or
       mixedcase names for variables since operators will always be in
       uppercase.

DDEEFF
       DDEEFF::_<_v_n_a_m_e_>=_<_r_r_d_f_i_l_e_>:_<_d_s_-_n_a_m_e_>:_<_C_F_>[:step=_<_s_t_e_p_>][:start=_<_t_i_m_e_>][:end=_<_t_i_m_e_>][:reduce=_<_CC_FF_>]

       This command fetches data from an RRRRDD file.  The virtual name _v_n_a_m_e can
       then be used throughout the rest of the script. By default, an RRRRAA
       which contains the correct consolidated data at an appropriate
       resolution will be chosen.  The resolution can be overridden with the
       --step option.  The resolution can again be overridden by specifying
       the sstteepp ssiizzee.  The time span of this data is the same as for the graph
       by default, you can override this by specifying ssttaarrtt aanndd eenndd.
       Remember to escape colons in the time specification!

       If the resolution of the data is higher than the resolution of the
       graph, the data will be further consolidated. This may result in a
       graph that spans slightly more time than requested.  Ideally each point
       in the graph should correspond with one CCDDPP from an RRRRAA.  For instance,
       if your RRRRDD has an RRRRAA with a resolution of 1800 seconds per CCDDPP, you
       should create an image with width 400 and time span 400*1800 seconds
       (use appropriate start and end times, such as "--start
       end-8days8hours").

       If consolidation needs to be done, the CCFF of the RRRRAA specified in the
       DDEEFF itself will be used to reduce the data density. This behaviour can
       be changed using ":reduce=_<CCFF_>_".  This optional parameter specifies the
       CCFF to use during the data reduction phase.

       Example:

               DEF:ds0=router.rrd:ds0:AVERAGE
               DEF:ds0weekly=router.rrd:ds0:AVERAGE:step=7200
               DEF:ds0weekly=router.rrd:ds0:AVERAGE:start=end-1h
               DEF:ds0weekly=router.rrd:ds0:AVERAGE:start=11\:00:end=start+1h

VVDDEEFF
       VVDDEEFF:_v_n_a_m_e=_R_P_N _e_x_p_r_e_s_s_i_o_n

       This command returns a value and/or a time according to the RRPPNN
       statements used. The resulting _v_n_a_m_e will, depending on the functions
       used, have a value and a time component.  When you use this _v_n_a_m_e in
       another RRPPNN expression, you are effectively inserting its value just as
       if you had put a number at that place.  The variable can also be used
       in the various graph and print elements.

       Example: "VDEF:avg=mydata,AVERAGE"

       Note that currently only aggregation functions work in VDEF rpn
       expressions.  Patches to change this are welcome.

CCDDEEFF
       CCDDEEFF:_v_n_a_m_e=_R_P_N _e_x_p_r_e_s_s_i_o_n

       This command creates a new set of data points (in memory only, not in
       the RRRRDD file) out of one or more other data series. The RRPPNN
       instructions are used to evaluate a mathematical function on each data
       point. The resulting _v_n_a_m_e can then be used further on in the script,
       just as if it were generated by a DDEEFF instruction.

       Example: "CDEF:mydatabits=mydata,8,*"

AAbboouutt CCDDEEFF vveerrssuuss VVDDEEFF
       At some point in processing, RRRRDDttooooll has gathered an array of rates
       ready to display.

       CCDDEEFF works on such an array.  For example, _C_D_E_F_:_n_e_w_=_d_s_0_,_8_,_* would
       multiply each of the array members by eight (probably transforming
       bytes into bits). The result is an array containing the new values.

       VVDDEEFF also works on such an array but in a different way.  For example,
       _V_D_E_F_:_m_a_x_=_d_s_0_,_M_A_X_I_M_U_M would scan each of the array members and store the
       maximum value.

   WWhheenn ddoo yyoouu uussee VVDDEEFF vveerrssuuss CCDDEEFF??
       Use CCDDEEFF to transform your data prior to graphing.  In the above
       example, we'd use a CCDDEEFF to transform bytes to bits before graphing the
       bits.

       You use a VVDDEEFF if you want _m_a_x_(_1_,_5_,_3_,_2_,_4_) to return five which would be
       displayed in the graph's legend (to answer, what was the maximum value
       during the graph period).

       If you want to apply 'complex' operations to the result of a VDEF you
       have to use a CDEF again since VDEFs only look like RPN expressions,
       they aren't realy.

SSEEEE AALLSSOO
       rrdgraph gives an overview of how rrrrddttooooll ggrraapphh works.  rrdgraph_data
       describes DDEEFF,CCDDEEFF and VVDDEEFF in detail.  rrdgraph_rpn describes the RRPPNN
       language used in the ??DDEEFF statements.  rrdgraph_graph page describes
       all of the graph and print functions.

       Make sure to read rrdgraph_examples for tips&tricks.

AAUUTTHHOORR
       Program by Tobias Oetiker <tobi@oetiker.ch>

       This manual page by Alex van den Bogaerdt <alex@vandenbogaerdt.nl> with
       corrections and/or additions by several people



1.3.9                             2009-04-29                  RRDGRAPH_DATA(1)
