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Dataplot Vol 1 Vol 2

READ PAD MISSING COLUMNS (SET)

Name:
    READ PAD MISSING COLUMNS (SET)
Type:
    Subcommand under SET
Purpose:
    If the number of variables specified on a READ command is greater than the number of values read from a data record, specify whether these extra values will be set to a specified "missing value" or this data record will be considered an error.
Description:
    By default, Dataplot considers a data record that returns fewer values than the number of variables specified on the READ command an error. This results in not only that particular data record being in error, but the entire READ is invalid.

    In some cases, it may be more convenient to assign a missing value to any variables that did not have a corresponding data item (e.g., if 8 variables were specified on the READ command and 5 items were detected on the data record, the data values would assigned to the first five variables on the READ and a missing value would be assigned to the remaining three variables.

    The default missing value is zero. You can specify the value to use for missing values with the command

      SET READ MISSING VALUE <value>

    This command is intended for the case when you expect data columns of equal length and you simply want to specify whether detecting an unequal column length will be treated as an error or not. If you know your data columns are of unequal length, you can either use a comma delimited file or use the variable form of the COLUMN LIMITS command. This is described in the Note: section below. In these cases, Dataplot will automatically handle missing data regardless of what the SET READ PAD MISSING COLUMNS specifies.

Syntax:
    SET READ PAD MISSING COLUMNS <ON/OFF> where ON specifies that missing columns will be padded with a missing data value and OFF specifies that missing columns will be treated as an error.
Examples:
    SET READ PAD MISSING COLUMN ON
    SET READ PAD MISSING COLUMN OFF
Note:
    If you know that your data contains columns of unequal length, there are several alternatives (in these cases, the SET READ PAD MISSING COLUMN ON command does not need to be entered).

    1. Pick some value to represent a missing value and fill in missing data points with that value. After reading the data, you can use a RETAIN command to remove them. For example, if you use -99 to signify a missing value, you can enter

        RETAIN Y SUBSET Y > -99

      Alternatively, you can use a SUBSET clause on subsequent plot and analysis commands.

      This is only a viable alternative if you have relatively few missing values in your file.

    2. Use the variable form of the COLUMN LIMITS command. This command allows you to specify the start and stop columns of each data field. By default, when a blank field is encountered, it is set to the missing value. This value can be set with the command

        SET READ MISSING VALUE <value>

      This option depends on having consistent columns for each of the data fields.

    3. If your data has both columns of unequal length and inconsistent columns for given data fields, an alternative is to use a comma delimited data file. That is, separate data values with a comma. If there is no data data between successive commas, this is treated as a missing value. The default is to assign a value of zero. Alternatively, you can use the SET READ MISSING VALUE command described above.

      You can specify a delimiter other than a comma with the command

        SET READ DELIMITER <character>

    In order to place data in the appropriate columns if we have data columns of unequal length, we either need to have consistent columns (we can use COLUMN LIMITS) or comma separated (or some other non-space delimiter) data. Otherwise Dataplot will not know how to assign the data values to the correct variable and it will simply assign data values to variables in the order the variables are found on the READ command.

Default:
    OFF (an insufficient number of data values on a data record is treated as an error).
Synonyms:
    None
Related Commands:
    READ = Carries out a column-wise input of data.
    COLUMN LIMITS = Specify what columns to read.
    SET READ MISSING VALUE = Specify the value used to denote a missing value.
    SET READ DELIMITER = Specify the character that will be interperted as a delimiter between fields on a data record.
Applications:
    Input/Output
Implementation Date:
    2004/10
Program:
     
    SET READ MISSING VALUE -99
    SET READ PAD MISSING COLUMN ON
    READ DUMMY.DAT  Y X
    RETAIN Y X SUBSET Y > -99 SUBSET X > -99
    PLOT Y X
        

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Date created: 12/05/2005
Last updated: 11/04/2015

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