


     RRRRRRRRDDDDGGGGRRRRAAAAPPPPHHHH____RRRRPPPPNNNN((((1111))))        1111....2222....11113333 ((((2222000000006666----00005555----00004444))))        RRRRRRRRDDDDGGGGRRRRAAAAPPPPHHHH____RRRRPPPPNNNN((((1111))))



     NNNNAAAAMMMMEEEE
          rrdgraph_rpn - About RPN Math in rrdtool graph

     SSSSYYYYNNNNOOOOPPPPSSSSIIIISSSS
          _R_P_N _e_x_p_r_e_s_s_i_o_n:=_v_n_a_m_e|_o_p_e_r_a_t_o_r|_v_a_l_u_e[,_R_P_N _e_x_p_r_e_s_s_i_o_n]

     DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
          If you have ever used a traditional HP calculator you
          already know RRRRPPPPNNNN. The idea behind RRRRPPPPNNNN is that you have a
          stack and push your data onto this stack. Whenever you
          execute an operation, 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 what is put into the _v_n_a_m_e.  For CCCCDDDDEEEEFFFF
          instructions, the stack is processed for each data point on
          the graph. VVVVDDDDEEEEFFFF instructions work on an entire data set in
          one run. Note, that currently VVVVDDDDEEEEFFFF instructions only support
          a limited list of functions.

          Example: "VDEF:maximum=mydata,MAXIMUM"

          This will set variable "maximum" which you now can use in
          the rest of your RRD script.

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

          This means:  push variable _m_y_d_a_t_a, push the number 8,
          execute the operator *. The operator needs two elements and
          uses those to return one value.  This value is then stored
          in _m_y_d_a_t_a_b_i_t_s.  As you may have guessed, this instruction
          means nothing more than _m_y_d_a_t_a_b_i_t_s = _m_y_d_a_t_a * _8.  The real
          power of RRRRPPPPNNNN lies in the fact that it is always clear in
          which order to process the input.  For expressions like "a =
          b + 3 * 5" you need to multiply 3 with 5 first before you
          add _b to get _a. However, with parentheses you could change
          this order: "a = (b + 3) * 5". In RRRRPPPPNNNN, you would do "a = b,
          3, +, 5, *" without the need for parentheses.

     OOOOPPPPEEEERRRRAAAATTTTOOOORRRRSSSS
          Boolean operators
              LLLLTTTT,,,, LLLLEEEE,,,, GGGGTTTT,,,, GGGGEEEE,,,, EEEEQQQQ,,,, NNNNEEEE

              Pop two elements from the stack, compare them for the
              selected condition and return 1 for true or 0 for false.
              Comparing an _u_n_k_n_o_w_n or an _i_n_f_i_n_i_t_e value will always
              result in 0 (false).

              UUUUNNNN,,,, IIIISSSSIIIINNNNFFFF



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     RRRRRRRRDDDDGGGGRRRRAAAAPPPPHHHH____RRRRPPPPNNNN((((1111))))        1111....2222....11113333 ((((2222000000006666----00005555----00004444))))        RRRRRRRRDDDDGGGGRRRRAAAAPPPPHHHH____RRRRPPPPNNNN((((1111))))



              Pop one element from the stack, compare this to _u_n_k_n_o_w_n
              respectively to _p_o_s_i_t_i_v_e _o_r _n_e_g_a_t_i_v_e _i_n_f_i_n_i_t_y. Returns 1
              for true or 0 for false.

              IIIIFFFF

              Pops three elements from the stack.  If the element
              popped last is 0 (false), the value popped first is
              pushed back onto the stack, otherwise the value popped
              second is pushed back. This does, indeed, mean that any
              value other than 0 is considered to be true.

              Example: "A,B,C,IF" should be read as "if (A) then (B)
              else (C)"



          Comparing values
              MMMMIIIINNNN,,,, MMMMAAAAXXXX

              Pops two elements from the stack and returns the smaller
              or larger, respectively.  Note that _i_n_f_i_n_i_t_e is larger
              than anything else.  If one of the input numbers is
              _u_n_k_n_o_w_n then the result of the operation will be _u_n_k_n_o_w_n
              too.

              LLLLIIIIMMMMIIIITTTT

              Pops two elements from the stack and uses them to define
              a range.  Then it pops another element and if it falls
              inside the range, it is pushed back. If not, an _u_n_k_n_o_w_n
              is pushed.

              The range defined includes the two boundaries (so: a
              number equal to one of the boundaries will be pushed
              back). If any of the three numbers involved is either
              _u_n_k_n_o_w_n or _i_n_f_i_n_i_t_e this function will always return an
              _u_n_k_n_o_w_n

              Example: "CDEF:a=alpha,0,100,LIMIT" will return _u_n_k_n_o_w_n
              if alpha is lower than 0 or if it is higher than 100.



          Arithmetics
              ++++,,,, ----,,,, ****,,,, ////,,,, %%%%

              Add, subtract, multiply, divide, modulo

              SSSSIIIINNNN,,,, CCCCOOOOSSSS,,,, LLLLOOOOGGGG,,,, EEEEXXXXPPPP,,,, SSSSQQQQRRRRTTTT

              Sine and cosine (input in radians), log and exp (natural



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     RRRRRRRRDDDDGGGGRRRRAAAAPPPPHHHH____RRRRPPPPNNNN((((1111))))        1111....2222....11113333 ((((2222000000006666----00005555----00004444))))        RRRRRRRRDDDDGGGGRRRRAAAAPPPPHHHH____RRRRPPPPNNNN((((1111))))



              logarithm), square root.

              AAAATTTTAAAANNNN

              Arctangent (output in radians).

              AAAATTTTAAAANNNN2222

              Arctangent of y,x components (output in radians).  This
              pops one element from the stack, the x (cosine)
              component, and then a second, which is the y (sine)
              component.  It then pushes the arctangent of their
              ratio, resolving the ambiguity between quadrants.

              Example: "CDEF:angle=Y,X,ATAN2,RAD2DEG" will convert
              "X,Y" components into an angle in degrees.

              FFFFLLLLOOOOOOOORRRR,,,, CCCCEEEEIIIILLLL

              Round down or up to the nearest integer.

              DDDDEEEEGGGG2222RRRRAAAADDDD,,,, RRRRAAAADDDD2222DDDDEEEEGGGG

              Convert angle in degrees to radians, or radians to
              degrees.

          Set Operations
              SSSSOOOORRRRTTTT,,,, RRRREEEEVVVV

              Pop one element from the stack.  This is the _c_o_u_n_t of
              items to be sorted (or reversed).  The top _c_o_u_n_t of the
              remaining elements are then sorted (or reversed) in
              place on the stack.

              Example:
              "CDEF:x=v1,v2,v3,v4,v5,v6,6,SORT,POP,5,REV,POP,+,+,+,4,/"
              will compute the average of the values v1 to v6 after
              removing the smallest and largest.

              TTTTRRRREEEENNNNDDDD

              Create a "sliding window" average of another data
              series.

              Usage:  CDEF:smoothed=x,1800,TREND

              This will create a half-hour (1800 second) sliding
              window average of x.  The average is essentially
              computed as shown here:






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     RRRRRRRRDDDDGGGGRRRRAAAAPPPPHHHH____RRRRPPPPNNNN((((1111))))        1111....2222....11113333 ((((2222000000006666----00005555----00004444))))        RRRRRRRRDDDDGGGGRRRRAAAAPPPPHHHH____RRRRPPPPNNNN((((1111))))



                               +---!---!---!---!---!---!---!---!--->
                                                                   now
                                     delay     t0
                               <--------------->
                                       delay       t1
                                   <--------------->
                                            delay      t2
                                       <--------------->

                   Value at sample (t0) will be the average between (t0-delay) and (t0)
                   Value at sample (t1) will be the average between (t1-delay) and (t1)
                   Value at sample (t2) will be the average between (t2-delay) and (t2)

          Special values
              UUUUNNNNKKKKNNNN

              Pushes an unknown value on the stack

              IIIINNNNFFFF,,,, NNNNEEEEGGGGIIIINNNNFFFF

              Pushes a positive or negative infinite value on the
              stack. When such a value is graphed, it appears at the
              top or bottom of the graph, no matter what the actual
              value on the y-axis is.

              PPPPRRRREEEEVVVV

              Pushes an _u_n_k_n_o_w_n value if this is the first value of a
              data set or otherwise the result of this CCCCDDDDEEEEFFFF at the
              previous time step. This allows you to do calculations
              across the data.  This function cannot be used in VVVVDDDDEEEEFFFF
              instructions.

              PPPPRRRREEEEVVVV((((vvvvnnnnaaaammmmeeee))))

              Pushes an _u_n_k_n_o_w_n value if this is the first value of a
              data set or otherwise the result of the vname variable
              at the previous time step. This allows you to do
              calculations across the data. This function cannot be
              used in VVVVDDDDEEEEFFFF instructions.

              CCCCOOOOUUUUNNNNTTTT

              Pushes the number 1 if this is the first value of the
              data set, the number 2 if it is the second, and so on.
              This special value allows you to make calculations based
              on the position of the value within the data set. This
              function cannot be used in VVVVDDDDEEEEFFFF instructions.

          Time
              Time inside RRDtool is measured in seconds since the
              epoch. The epoch is defined to be



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     RRRRRRRRDDDDGGGGRRRRAAAAPPPPHHHH____RRRRPPPPNNNN((((1111))))        1111....2222....11113333 ((((2222000000006666----00005555----00004444))))        RRRRRRRRDDDDGGGGRRRRAAAAPPPPHHHH____RRRRPPPPNNNN((((1111))))



              "Thu Jan 1 00:00:00 UTC 1970".

              NNNNOOOOWWWW

              Pushes the current time on the stack.

              TTTTIIIIMMMMEEEE

              Pushes the time the currently processed value was taken
              at onto the stack.

              LLLLTTTTIIIIMMMMEEEE

              Takes the time as defined by TTTTIIIIMMMMEEEE, applies the time zone
              offset valid at that time including daylight saving time
              if your OS supports it, and pushes the result on the
              stack.  There is an elaborate example in the examples
              section below on how to use this.

          Processing the stack directly
              DDDDUUUUPPPP,,,, PPPPOOOOPPPP,,,, EEEEXXXXCCCC

              Duplicate the top element, remove the top element,
              exchange the two top elements.



     VVVVAAAARRRRIIIIAAAABBBBLLLLEEEESSSS
          These operators work only on VVVVDDDDEEEEFFFF statements. Note that
          currently ONLY these work for VVVVDDDDEEEEFFFF.

          MAXIMUM, MINIMUM, AVERAGE
              Return the corresponding value, MAXIMUM and MINIMUM also
              return the first occurrence of that value in the time
              component.

              Example: "VDEF:avg=mydata,AVERAGE"

          LAST, FIRST
              Return the last/first value including its time.  The
              time for FIRST is actually the start of the
              corresponding interval, whereas LAST returns the end of
              the corresponding interval.

              Example: "VDEF:first=mydata,FIRST"

          TOTAL
              Returns the rate from each defined time slot multiplied
              with the step size.  This can, for instance, return
              total bytes transfered when you have logged bytes per
              second. The time component returns the number of
              seconds.



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     RRRRRRRRDDDDGGGGRRRRAAAAPPPPHHHH____RRRRPPPPNNNN((((1111))))        1111....2222....11113333 ((((2222000000006666----00005555----00004444))))        RRRRRRRRDDDDGGGGRRRRAAAAPPPPHHHH____RRRRPPPPNNNN((((1111))))



              Example: "VDEF:total=mydata,TOTAL"

          PERCENT
              This should follow a DDDDEEEEFFFF or CCCCDDDDEEEEFFFF _v_n_a_m_e. The _v_n_a_m_e 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 _p_e_r_c_e_n_t_a_g_e percent of
              the values is lower or equal than the result.  _U_n_k_n_o_w_n
              values are considered lower than any finite number for
              this purpose so if this operator returns an _u_n_k_n_o_w_n you
              have quite a lot of them in your data.  IIIInnnnffffinite numbers
              are lesser, or more, than the finite numbers and are
              always more than the _U_n_k_n_o_w_n numbers.  (NaN < -INF <
              finite values < INF)

              Example: "VDEF:perc95=mydata,95,PERCENT"

          LSLSLOPE, LSLINT, LSLCORREL
              Return the parameters for a LLLLeast SSSSquares LLLLine (_y = _m_x
              +_b) which approximate the provided dataset.  LSLSLOPE is
              the slope (_m) of the line related to the COUNT position
              of the data.  LSLINT is the y-intercept (_b), which
              happens also to be the first data point on the graph.
              LSLCORREL is the Correlation Coefficient (also know as
              Pearson's Product Moment Correlation Coefficient).  It
              will range from 0 to +/-1 and represents the quality of
              fit for the approximation.

              Example: "VDEF:slope=mydata,LSLSLOPE"

     SSSSEEEEEEEE AAAALLLLSSSSOOOO
          rrdgraph gives an overview of how rrrrrrrrddddttttoooooooollll ggggrrrraaaapppphhhh works.
          rrdgraph_data describes DDDDEEEEFFFF,CCCCDDDDEEEEFFFF and VVVVDDDDEEEEFFFF in detail.
          rrdgraph_rpn describes the RRRRPPPPNNNN language used in the ????DDDDEEEEFFFF
          statements.  rrdgraph_graph page describes all of the graph
          and print functions.

          Make sure to read rrdgraph_examples for tips&tricks.

     AAAAUUUUTTTTHHHHOOOORRRR
          Program by Tobias Oetiker <tobi@oetiker.ch>

          This manual page by Alex van den Bogaerdt
          <alex@ergens.op.het.net>











     Page 6                                          (printed 6/13/06)



