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Dataplot Vol 1 Auxiliary Chapter

MAXIMUM RECORD LENGTH

Name:
    MAXIMUM RECORD LENGTH
Type:
    Support Command
Purpose:
    Specifies the maximum size record that can be read during subsequent READ and SERIAL READ commands.
Description:
    Prior to the 2/2003 version, Dataplot would read 132 columns from external data files. The COLUMN LIMITS could be used to specify which columns between 1 and 132 were read, but it could not specify columns past 132. The only way around this restriction was to use the SET READ FORMAT command (i.e., specify a Fortran-like format statement for the read). However, this required a fixed and consistent format for the data (and the user had to know what that format was).

    The MAXIMUM RECORD LENGTH command can now be used to specify a maximum record length for data files. This record length can be any value between 132 (if you request a value less than 132, the maximum record length will be set to 132) and a maximum record length (currently set to 9999).

    Also, the default maximum record length has been increased from 132 to 255.

    If you specify a maximum record length greater than 255, you still need to enter a COLUMN LIMITS command to access those columns.

Syntax:
    MAXIMUM RECORD LENGTH <value>
    where <value> is a number or parameter between 132 and 9999 that specifies the desired maximum record length.

    Entering AUTO, OM, OFF, or DEFAULT will reset the default value (255). Entering a question mark ("?") will print the current value and the default value for the maximum record length.

Examples:
    MAXIMUM RECORD LENGTH 500
    MAXIMUM RECORD LENGTH 132
    MAXIMUM RECORD LENGTH DEFAULT
Note:
    This command specifies the number of characters that are read from a data record. Be aware that some Fortran compilers may have their own limit for the maximum record length (this value does not tend to be well documented by most Fortran compilers). Dataplot currently does not try to determine if the given Fortran compiler limit has been exceeded.

    Some Fortran compilers allow you to up this limit when you open the file. However, this option is not part of the Fortran standard (and is not available on all Fortran compilers). For now, Dataplot does not use the maximum record length when opening the file. As we gain more experience with this capability, we may add the maximum record length when opening the data file.

    This should rarely be an issue. The Fortran compiler limit, if it exists, tends to be rather large. Unless your data records exceed 750 columns, you are unlikely to run into this limitation.

Note:
    This command only applies to data read from external files. Reads from the terminal are still restricted to a maximum of 80 columns.
Default:
    DATAPLOT reads columns 1 to 255.
Synonyms:
    None
Related Commands:
    READ = Reads data (column-wise) into variables.
    SERIAL READ = Reads data (row-wise) into variables.
    ROW LIMITS = Sets file lines to be included in read.
    SKIP = Sets the number of lines to skip over at the beginning of a file in subsequent reads.
    SET READ FORMAT = Defines a Fortran like format to use in subsequent reads.
    COLUMN LIMITS = Sets the columns to be included in read.
Applications:
    Data Input
Implementation Date:
    2/2003
Program:
 
    DIMENSION 100 VARIABLES
    .
    .  Write out some data with long records
    .
    LET XTEMP = SEQUENCE 1 1 20
    LOOP FOR K = 1 1 50
        LET X^K = K*XTEMP
    END OF LOOP
    .
    SET WRITE FORMAT (50f10.0)
    WRITE TEST.OUT X1 TO X50
    .
    .  Now, read them back in
    .
    MAXIMUM RECORD LENGTH 600
    COLUMN LIMITS 1 600
    RESET DATA
    READ TEST.OUT Y1 TO Y50
    

Date created: 2/13/2003
Last updated: 4/4/2003
Please email comments on this WWW page to alan.heckert@nist.gov.