Teradata R Package Function Reference - 16.20 - Unpack - Teradata R Package

Teradata® R Package Function Reference

prodname
Teradata R Package
vrm_release
16.20
created_date
February 2020
category
Programming Reference
featnum
B700-4007-098K

Description

The Unpack function unpacks data from a single packed column into multiple columns. The packed column is composed of multiple virtual columns, which become the output columns. To determine the virtual columns, the function must have either the delimiter that separates them in the packed column or their lengths.

Usage

  td_unpack_mle (
      data = NULL,
      input.column = NULL,
      output.columns = NULL,
      output.datatypes = NULL,
      delimiter = ",",
      column.length = NULL,
      regex = "(.*)",
      regex.set = 1,
      exception = FALSE
  )

Arguments

data

Required Argument.
Specifies the tbl_teradata containing the input attributes.

input.column

Required Argument.
Specifies the name of the input column that contains the packed data.

output.columns

Required Argument.
Specifies the names to give to the output columns, in the order in which the corresponding virtual columns appear in input_column.

output.datatypes

Required Argument.
Specifies the datatypes of the unpacked output columns. If output.datatypes specifies only one value and output.columns specifies multiple columns, then the specified value applies to every output_column. If output.datatypes specifies multiple values, then it must specify a value for each output_column. The nth datatype corresponds to the nth output_column.

delimiter

Optional Argument.
Specifies the delimiter (a string) that separates the virtual columns in the packed data. If the delimiter contains a character that is a symbol in a regular expression, such as, an asterisk (*) or pipe character (|) then precede it with two escape characters. For example, if the delimiter is the pipe character, specify "\|". The default delimiter is comma (,). If the virtual columns are separated by a delimiter, then specify the delimiter with this argument; otherwise, specify the column.length argument. Do not specify both of these arguments and the column.length argument.
Default Value: ","

column.length

Optional Argument.
Specifies the lengths of the virtual columns. To use this argument, you must know the length of each virtual column. If column.length specifies only one value and output.columns specifies multiple columns, then the specified value applies to every output_column. If column.length specifies multiple values, then it must specify a value for each output_column. The nth datatype corresponds to the nth output_column. However, the last column_name can be an asterisk (*), which represents a single virtual column that contains the remaining data. For example, if the first three virtual columns have the lengths 2, 1, and 3, and all remaining data belongs to the fourth virtual column, you can specify column.length ("2", "1", "3", *). If you specify this argument, you must omit the delimiter argument.

regex

Optional Argument.
Specifies a regular expression that describes a row of packed data, enabling the function to find the data values. A row of packed data contains one data value for each virtual column, but the row might also contain other information (such as the virtual column name). In the regular_expression, each data value is enclosed in parentheses. For example, suppose that the packed data has two virtual columns, age and sex, and that one row of packed data is: age:34,sex:male The regular_expression that describes the row is ".*:(.*)". The ".*:" matches the virtual column names, age and sex, and the "(.*)" matches the values, 34 and male. The default regular_expression is "(.*)" which matches the whole string (between delimiters, if any). When applied to the preceding sample row, the default regular_expression causes the function to return "age:34" and "sex:male" as data values. To represent multiple data groups in regular_expression, use multiple pairs of parentheses. By default, the last data group in regular_expression represents the data value (other data groups are assumed to be virtual column names or unwanted data). If a different data group represents the data value, specify its group number with the regex.set argument.
Default Value: "(.*)"

regex.set

Optional Argument.
Specifies the ordinal number of the data group in regular_expression that represents the data value in a virtual column. By default, the last data group in regular_expression represents the data value. For example, suppose that regular_expression is: "([a-zA-Z]*):(.*)" If group_number is "1", then "([a-zA-Z]*)" represents the data value. If group_number is "2", then "(.*)" represents the data value.
Default Value: 1

exception

Optional Argument.
Specifies whether the function ignores rows that contain invalid data, that is, continues without outputting them. which causes the function to fail if it encounters a row with invalid data.
Default Value: FALSE

Value

Function returns a named list containing Teradata tbl object.
Named list member can be referenced directly with the "$" operator using name: result

Examples

    # Get the current context/connection
    con <- td_get_context()$connection
    
    # Load example data.
    loadExampleData("unpack_example", "ville_tempdata", "ville_tempdata1")
    
    # Create remote tibble objects.
    ville_tempdata <- tbl(con, "ville_tempdata")
    ville_tempdata1 <- tbl(con, "ville_tempdata1")
    
    # Example 1 -
    td_unpack_out1 <- td_unpack_mle(data = ville_tempdata,
                        input.column = "packed_temp_data",
                        output.columns = c("city","state","temp_F"),
                        output.datatypes = c("varchar","varchar","real"),
                        delimiter = ",",
                        regex = '(.*)',
                        regex.set = 1,
                        exception = TRUE
                        )
    
    # Example 2 -
    td_unpack_out2 <- td_unpack_mle(data = ville_tempdata1,
                        input.column = "packed_temp_data",
                        output.columns = c("city","state","temp_F"),
                        output.datatypes = c("varchar","varchar","real"),
                        column.length = c("9","9","4"),
                        regex = '(.*)',
                        regex.set = 1,
                        exception = TRUE
                        )