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Dataplot Vol 2 Vol 1

ABRAM

Name:
    ABRAM (LET)
Type:
    Library Function
Purpose:
    Compute the Abramowitz function.
Description:
    The Abramowitz function is defined as:

      f(x,m) = INTEGRAL[t**m*EXP(-t**2 -x/t)dt],   x >= 0

    where the integral is defined from 0 to positive infinity and m, a non-negative integer, is the order of the Abramowitz function. Dataplot supports values of m from 0 to 100.

    For m > 2, the following recurrence formula is used:

      2f(m) = (m-1)*f(m-2) + x*f(m-3)

    Dataplot computes this function using ACM Algorithm 757 (see Reference: below).

Syntax:
    LET <y> = ABRAM(<x>,<ord>) <SUBSET/EXCEPT/FOR qualification>
    where <x> is a non-negative number, variable or parameter;
              <ord> is a non-negative integer number, parameter, or variable in the range 0 to 100;
              <y> is a variable or a parameter (depending on what <x> and <ord> are) where the computed Abramowitz function values are stored;
    and where the <SUBSET/EXCEPT/FOR qualification> is optional.
Examples:
    LET A = ABRAM(2.3,1)
    LET A = ABRAM(X,A1)
    LET X2 = ABRAM(X1,4) FOR X1 = 0.1 0.1 3.0
Note:
    Library functions are distinguished from let subcommands in the following ways.
    1. Functions enclose the input value in parenthesis. Let subcommands use spaces.

    2. Functions can accept (and return) either parameters (i.e., single values) or variables (i.e., an array of values) while let subcommands are specific in which they accept as input and what they return as output.

    3. Functions can accept expressions while let subcommands do not. For example, the following is legal:

        LET Y2 = ABS(Y1-INT(Y1))

      For let subcommands, you typically have to do something like the following:

        LET YTEMP = Y**2 + 8
        LET A = SUM YTEMP
Default:
    None
Synonyms:
    None
Related Commands:
    CLAUSN = Compute the Clausen integral.
    DEBEYE = Compute the Debeye function.
    EXP3 = Compute the cubic exponential integral.
    GOODST = Compute the Goodwin and Stanton integral.
    LOBACH = Compute the Lobachevski integral.
    SYNCH1 = Compute the synchrotron radiation function.
    SYNCH2 = Compute the synchrotron radiation function.
    STROM = Compute the Stromgren integral.
    TRAN = Compute the transport integral.
Reference:
    "ACM Transactions of Mathematical Software", Allan MacLead, Vol. 22, No. 3, September, 1996, pp. 288-301.
Applications:
    Special Functions
Implementation Date:
    1999/6
Program:
    MULTIPLOT 2 2
    MULTIPLOT CORNER COORDINATES 5 5 95 95
    YLIMITS 0 1
    TITLE ORDER 0
    PLOT ABRAM(X,0) FOR X = 0 0.01 5
    TITLE ORDER 1
    PLOT ABRAM(X,1) FOR X = 0 0.01 5
    TITLE ORDER 2
    PLOT ABRAM(X,2) FOR X = 0 0.01 5
    TITLE ORDER 3
    PLOT ABRAM(X,3) FOR X = 0 0.01 5
    END OF MULTIPLOT
    MOVE 50 97
    JUSTIFICATION CENTER
    TEXT ABRAMOWITZ FUNCTIONS

    plot generated by sample program

Date created: 6/5/2001
Last updated: 4/4/2003
Please email comments on this WWW page to alan.heckert@nist.gov.