1 Numbers

  In most places when  Mn_Fit asks for a number,  such as a cut or the bin
  limits for a new plot  or the axis label  parameters you can give one of
  the following possibilities.

  Certain character variables can also be given - an array of character
  strings (`CHAR') histogram titles (`CHTITLE') and Ntuple variable names
  (`CHNAME') and/or the values (`CHVAL') of character
  variables - see HELP Text for more details. These are mostly useful for
  messages and for manipulating histogram titles when making projections of
  Ntuples. They could also be useful to translate from ROOT string histogram
  identifiers to Mn_Fit numerical identifiers.

  In addition you can define new variable names using the command `DEPOSIT'
  and these can then be used in the same way. The variable names must be
  alphanumeric expressions including `$' and `_', of maximum length 8
  characters. Variable names which match one of the names below (e.g. R, ERR),
  or a FORTRAN intrinsic function are not allowed nor is the name `ALL'. The
  names are converted to upper case. If you want to be able to treat the
  variables as an integer they should start with a letter between `I' and
  `N'. The new variables can be deleted using the `REMOVE' command.  See HELP
  DEPOSIT for more details: e.g. dep pi = 3.14159 dep r2 = sin(pi/2)

  These extra variables are stored in registers >300. You can look at
  the values of registers, parameters, bin contents etc. using the
  `EXAMINE' command or the `SHOW REGISTER' command for registers only.

  Note that numbers are always floating point, with the exception of `IR'.

    A number, e.g. 4, -5.2, 3.2E+02. It is not necessary to give the
      decimal point for real numbers.

    A register
      Rn or IRn where n can be from 0 to 500.
         Note that you are allowed to fill registers 0-99 with
         whatever you wish using the `DEPOSIT' command. All register contents
         are stored as real numbers. The integer format `IR' is used when
         you want to convert the contents to an integer to put them in
         a text string (see HELP Text).
         Registers 100 and above contain the following information:
          101  The result of a `SUM' or `INTEGRATE' command
          102  The number of points summed over in `SUM'
          111  The chi**2 or likelihood from the fit
          112  The confidence level of a fit
          113  The fit status (3 means converged properly)
          114  The EDM (estimated distance to minimum) of the fit

         Registers 121 onwards are filled if you give the command
         `SET PLOT id [&idb] DEFAULT' or `SET HISTOGRAM id':
          121  The plot identifier
          122  The secondary plot identifier
          123  The number of entries (histograms) or points
          124  The dimension of the plot (positive for histograms,
               negative for Ntuples and a series of points).
          125  The area under the plot (i.e. sum of weights)
          126  The minimum number of entries (weight)
          127  The maximum number of entries (weight)
          128  The creation date of the histogram (yymmdd)
          129  The creation time of the histogram (hhmm)
          131  The number of bins on x-axis (0 for Ntuples and points)
          132  The lower limit of the x-axis
          133  The upper limit of the x-axis
          134  The mean value for the x-axis
          135  The sigma for the x-axis
          136  The number of bins on y-axis (0 for Ntuples and points)
          137  The lower limit of the y-axis
          138  The upper limit of the y-axis
          139  The mean value for the y-axis
          140  The sigma for the y-axis
          etc. up to 14th dimension of an Ntuple.

         Registers 201-204 contain the positions of the corners of the
         current plot in cm:
          201  x position left
          202  x position right
          203  y position bottom
          204  y position top

         Registers 205-210 contain the limits used for the drawing of
         each of the axes in plot coordinates:
          205  x minimum
          206  x maximum
          207  y minimum
          208  y maximum
          209  z minimum
          210  z maximum

         Registers 231-257 contain total contents, as well as
         underflows and overflows of the default histogram:
          231  Underflows x-axis
          232  Contents x-axis
          233  Overflows x-axis

         For 2 dimensional histograms 9 registers are filled contents
         in register 235), while for 3-dimensional histograms 27
         registers are filled (contents in register 244).

         Registers > 300 contain the values of the extra variables that
         you have defined.

    A parameter, its parabolic error, or its positive or negative error,
    or its limits.
    The syntax to use is:
      Pn(m)     for the parameter
      ERRn(m)   for the parabolic error on the parameter
      ERNn(m)   for the negative MINOS error on the parameter
      ERPn(m)   for the positive MINOS error on the parameter
      LOLIMn(m) for the lower limit on the parameter value
      HILIMn(m) for the upper limit on the parameter value
    where n is the function number and m is the parameter number

    The centre of a bin, the bin width, the contents or the error on the
    contents (including asymmetric errors). The syntax to use is:
      Xn(m)     for the bin centre or the x value of a point
      Yn(m)     for the bin contents.
      DXn(m)    for half the bin width or the error on the x value
      DYn(m)    for the error on the y value
      DNXn(m)   for half the bin width or the negative error on the x value
      DNYn(m)   for the negative error on the y value
      DPXn(m)   for half the bin width or the positive error on the x value
      DPYn(m)   for the positive error on the y value
    where n is the plot number (including the optional secndary identifier
    if needed).
    For 2-dimensional histograms give both bin numbers. e.g. Xn(l,m).
    However note that it is not possible to use the Y value of a bin a Y
    ALWAYS means the bin contents for histograms. You can always calculate
    the y value of a particular bin or the y bin width using registers
    134,135 and 136.
    For plots with asymmetric errors `DX' and `DY' are interpreted as
    the negative errors if you want to get the value and as both
    errors if you are using the `DEPOSIT' command.

    The value of an Ntuple variable. The syntax to use is:
      Xn(m,nvar) or
      Xn(m,tvar) where n is the plot number, m is the event number
                 nvar is the variable number and tvar is the variable name.
    For cuts and expressions for projections you can just give the variable
    name. Within the `DEPOSIT' command you can access CWN variables,
    but not arrays.

  If the plot identifier is stored in a register, use the \texttt{PARSE}
  command to convert it into a number.

  In general if you want to keep the current value of a number use the `='
  sign. You can also add, subtract, multiply or divide the current value
  by using the syntax `=+1.0, =*R2', etc.

