NAME

       gmtmath - Reverse Polish Notation calculator for data tables


SYNOPSIS

       gmtmath [ -Ccols ] [ -Hnrec ] [ -Nn_col/t_col ] [ -Q ]
        [ -S ][ -Tt_min/t_max/t_inc ] [ -V ] [ -bi[s][n] ] [ -bo[s][n] ] oper-
       and [ operand ] OPERATOR [ operand ] OPERATOR ... = [ outfile ]


DESCRIPTION

       gmtmath will perform  operations  like  add,  subtract,  multiply,  and
       divide  on one or more table data files or constants using Reverse Pol-
       ish Notation (RPN)  syntax  (e.g.,  Hewlett-Packard  calculator-style).
       Arbitrarily  complicated  expressions  may  therefore be evaluated; the
       final result is written to an output file [or standard  output].   When
       two data tables are on the stack, each element in file A is modified by
       the corresponding element in file  B.   However,  some  operators  only
       require  one  operand  (see  below).  If no data tables are used in the
       expression then options -T, -N must be set  (and  optionally  -b).   By
       default, all columns except the "time" column are operated on, but this
       can be changed (see -C).

       operand
              If operand can be opened as a file it will be read as  an  ASCII
              (or  binary,  see  -bi)  table  data file.  If not a file, it is
              interpreted as a numerical constant or  a  special  symbol  (see
              below).

       outfile  is  a table data file that will hold the final result.  If not
       given then
              the output is sent to stdout.

       OPERATORS
              Choose among the following operators:
              Operator       n_args    Returns

              ABS       1    abs (A).
              ACOS      1    acos (A).
              ACOSH          1    acosh (A).
              ADD(+)         2    A + B.
              AND       2    NaN if A and B == NaN, B if A == NaN, else A.
              ASIN      1    asin (A).
              ASINH          1    asinh (A).
              ATAN      1    atan (A).
              ATAN2          2    atan2 (A, B).
              ATANH     1    atanh (A).
              BEI       1    bei (A).
              BER       1    ber (A).
              CEIL      1    ceil (A) (smallest integer >= A).
              CHIDIST        2    Chi-squared-distribution   P(chi2,nu),  with
              chi2 = A and nu = B.
              COS       1    cos (A) (A in radians).
              COSD      1    cos (A) (A in degrees).
              COSH      1    cosh (A).
              D2DT2          1    d^2(A)/dt^2 2nd derivative.
              D2R       1    Converts Degrees to Radians.
              DILOG          1    Dilog (A).
              DIV(/)         2    A / B.
              DDT       1    d(A)/dt 1st derivative.
              DUP       1    Places duplicate of A on the stack.
              ERF       1    Error function of A.
              ERFC      1    Complementory Error function of A.
              ERFINV         1    Inverse error function of A.
              EQ        2    1 if A == B, else 0.
              EXCH      2    Exchanges A and B on the stack.
              EXP       1    exp (A).
              FDIST          4    F-dist Q(var1,var2,nu1,nu2), with var1 =  A,
              var2 = B, nu1 = C, and nu2 = D.
              FLOOR          1    floor (A) (greatest integer <= A).
              FMOD      2    A % B (remainder).
              GE        2    1 if A >= B, else 0.
              GT        2    1 if A > B, else 0.
              HYPOT          2    hypot (A, B).
              I0        1    Modified  Bessel  function  of A (1st kind, order
              0).
              I1        1    Modified Bessel function of A  (1st  kind,  order
              1).
              IN        2    Modified  Bessel  function  of A (1st kind, order
              B).
              INT       1    Numerically integrate A.
              INV       1    1 / A.
              ISNAN          1    1 if A == NaN, else 0.
              J0        1    Bessel function of A (1st kind, order 0).
              J1        1    Bessel function of A (1st kind, order 1).
              JN        2    Bessel function of A (1st kind, order B).
              K0        1    Modified Kelvin function of A  (2nd  kind,  order
              0).
              K1        1    Modified  Bessel  function  of A (2nd kind, order
              1).
              KN        2    Modified Bessel function of A  (2nd  kind,  order
              B).
              KEI       1    kei (A).
              KER       1    ker (A).
              LE        2    1 if A <= B, else 0.
              LMSSCL         1    LMS scale estimate (LMS STD) of A.
              LOG       1    log (A) (natural log).
              LOG10          1    log10 (A).
              LOG1P          1    log (1+A) (accurate for small A).
              LOWER          1    The lowest (minimum) value of A.
              LT        2    1 if A < B, else 0.
              MAD       1    Median Absolute Deviation (L1 STD) of A.
              MAX       2    Maximum of A and B.
              MEAN      1    Mean value of A.
              MED       1    Median value of A.
              MIN       2    Minimum of A and B.
              MODE      1    Mode value (LMS) of A.
              MUL(x)         2    A * B.
              NAN       2    NaN if A == B, else A.
              NEG       1    -A.
              NRAND          2    Normal,  random  values with mean A and std.
              deviation B.
              OR        2    NaN if A or B == NaN, else A.
              PLM       3    Associated Legendre polynomial P(-1<A<+1)  degree
              B order C.
              POP       1    Delete top element from the stack.
              POW(^)         2    A ^ B.
              R2        2    R2 = A^2 + B^2.
              R2D       1    Convert Radians to Degrees.
              RAND      2    Uniform random values between A and B.
              RINT      1    rint (A) (nearest integer).
              SIGN      1    sign (+1 or -1) of A.
              SIN       1    sin (A) (A in radians).
              SIND      1    sin (A) (A in degrees).
              SINH      1    sinh (A).
              SQRT      1    sqrt (A).
              STD       1    Standard deviation of A.
              STEP      1    Heaviside step function H(A).
              STEPT          1    Heaviside step function H(t-A).
              SUB(-)         2    A - B.
              SUM       1    Cumulative sum of A
              TAN       1    tan (A) (A in radians).
              TAND      1    tan (A) (A in degrees).
              TANH      1    tanh (A).
              TDIST          2    Student's  t-distribution  A(t,nu) = 1 - 2p,
              with t = A, and nu = B.
              UPPER          1    The highest (maximum) value of A.
              XOR       2    B if A == NaN, else A.
              Y0        1    Bessel function of A (2nd kind, order 0).
              Y1        1    Bessel function of A (2nd kind, order 1).
              YN        2    Bessel function of A (2nd kind, order B).

       SYMBOLS
              The following symbols have special meaning:

              PI   3.1415926...
              E    2.7182818...
              T    Table with t-coordinates


OPTIONS

       -C     Select the columns that will be operated on  until  next  occur-
              rence  of  -C.   List  columns  separated by commas; ranges like
              1,3-5,7 are allowed.  [-C  (no  arguments)  resets  the  default
              action  of  using  all columns except time column (see -N].  -Ca
              selects all columns, inluding time column,  while  -Cr  reverses
              (toggles) the current choices.

       -H     Input  file(s)  has  Header record(s).  Number of header records
              can be changed by editing your .gmtdefaults file.  If used,  GMT
              default is 1 header record.

       -N     Select the number of columns and the column number that contains
              the "time" variable.  Columns are numbered starting at 0  [2/0].

       -Q     Quick  mode  for  scalar  calculation.   Shorthand for -Ca -N1/0
              -T0/0/1.

       -S     Only report the first row of the results [Default is all  rows].
              This  is  useful if you have computed a statistic (say the MODE)
              and only want to report a  single  number  instead  of  numerous
              records with idendical values.

       -T     Required  when no input files are given.  Sets the t-coordinates
              of the first and last point and the equidistant sampling  inter-
              val  for the "time" column (see -N).  If there is no time column
              (only data columns),  give  -T  with  no  arguments;  this  also
              implies -Ca.

       -V     Selects verbose mode, which will send progress reports to stderr
              [Default runs "silently"].

       -bi    Selects binary input.  Append s for single precision [Default is
              double].   Append  n  for  the  number  of columns in the binary
              file(s).

       -O     Selects Overlay plot mode [Default initializes a new  plot  sys-
              tem].


BEWARE

       The  operator  PLM  calculates  the  associated  Legendre polynomial of
       degree L and order M, and its argument is the cosine of the  colatitude
       which must satisfy -1 <= x <= +1. PLM is not normalized.
       All  derivatives  are based on central finite differences, with natural
       boundary conditions.


EXAMPLES

       To take log10 of the average of 2 data files, use
            gmtmath file1.d file2.d ADD 0.5 MUL LOG10 = file3.d

       Given the file  samples.d,  which  holds  seafloor  ages  in  m.y.  and
       seafloor  depth  in m, use the relation depth(in m) = 2500 + 350 * sqrt
       (age) to print the depth anomalies:
            gmtmath samples.d T SQRT 350 MUL 2500 ADD SUB = | lpr

       To take the average of columns  1  and  4-6  in  the  three  data  sets
       sizes.1, sizes.2, and sizes.3, use
            gmtmath -C1,4-6 sizes.1 sizes.2 ADD sizes.3 ADD 3 DIV = ave.d

       To  take the 1-column data set ages.d and calculate the modal value and
       assign it to a variable, try
            set mode_age = `gmtmath -S -T ages.d MODE =`

       To use gmtmath as a RPN Hewlett-Packard calculator on scalars (i.e., no
       input  files)  and  calculate arbitrary expressions, use the -Q option.
       As an example, we will calculate the value of Kei (((1 +  1.75)/2.2)  +
       cos (60)) and store the result in the shell variable z:

            set z = `gmtmath -Q 1 1.75 ADD 2.2 DIV 60 COSD ADD KEI =`


BUGS

       Files  that  have  the same name as some operators, e.g., ADD, SIGN, =,
       etc. cannot be read and must not be present in the  current  directory.
       Piping  of files is not allowed on input, but the output can be sent to
       stdout.  The stack limit is hard-wired to 50.  All functions  expecting
       a  positive radius (e.g., log, kei, etc.) are passed the absolute value
       of their argument.


REFERENCES

       Abramowitz, M., and I. A. Stegun, 1964, Handbook of Mathematical  Func-
       tions, Applied Mathematics Series, vol. 55, Dover, New York.
       Press, W. H.,  S. A. Teukolsky, W. T. Vetterling, B. P. Flannery, 1992,
       Numerical Recipes, 2nd edition, Cambridge Univ., New York.


SEE ALSO

       gmt(l), grd2xyz(l), grdedit(l), grdinfo(l), grdmath(l), xyz2grd(l)



VERSION                              DATE                           GMTMATH(l)

Man(1) output converted with man2html