Generates bitvectors either from a table containing numerical values, or from a string column containing the bit positions to set, hexadecimal or binary strings.

Numeric input (many columns)

In the case of a numerical input the columns correspond to the bit positions in the resulting bitvector, i.e. if only one numerical column is available all bitvectors will have length 1. All numeric columns in the table are considered. There are two options to determine if the bit is set for the value in the corresponding column or not:

• either a global threshold is defined, then all values which are above or equal to the threshold are converted into set bits, all other bit positions remain 0, or
• a certain percentage of the mean of each column is used as a threshold, then all values which are above or equal to the percentage of the mean are converted into set bits.

Strings (one column)

In the case of a string input only the column containing the string is considered for the generation of the bitvectors. The string is parsed and converted into a bitvector. There are three valid input formats which can be parsed and converted:

• Hexadecimal strings: strings consisting only of the characters 0-9 and A - F (where lower- or uppercase is not important). The represented hexadecimal number is converted into a binary number which is represented by the resulting bitvector.
• Binary strings: strings consisting only of 0s and 1s are parsed and converted into the according bitvectors.
• ID strings: strings consisting of numbers (separated by spaces) where the numbers refer to those positions in the bitvector which should be set. (Typical input format for association rule mining).

Missing values

For numeric data the incoming missing values will result in 0s. For the string input missing values will also result in a missing value in the output table. If a string could not be parsed it will also result in a missing cell in the output table.

Options

Numeric input

Select if several numeric columns should be converted into a bitvector.

Threshold

If the "numeric input" is checked, specify the global threshold. All values which are above or equal to this threshold will result in a 1 in the bitvector.

Use percentage of the mean

Check, if a percentage of the mean of each column should serve as threshold above which the bits are set.

Percentage

Specify which percentage of the mean a value should have in order to be set.

Parse bitvectors from string column

Check, if the input for the bitvectors is a string column that should be converted into a bitvector (see description above for valid input formats). Uncheck, if the data is a table with numerical data that should be converted into bitvectors. All numerical columns will be considered, all others are irgnored.

String column to be parsed

If the "parse from string column" is checked, select the column containing the strings.

Kind of string representation

Select one of the three valid input formats: HEX (hexadecimal), ID (bit positions) or BIT (binary strings). See description above.

Remove column(s) used for bit vector creation:

If it is checked the generating column(s) (included columns if numeric input was used or the selected string column) are removed. If it is unchecked the generated bitvectors are appended to the input table.

Views

Statistics View

Provides information about the generation of the bitvectors from the data. In particular this is the number of processed rows, the total number of generated zeros and ones and the resulting ratio of 1s to 0s.

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