Datasets and Attributes

Datasets

Every process created in Rulex starts from one or more specific datasets, each of which contains the sample of observations for a system or a problem.

A dataset has a tabular form, where each row corresponds to an example (or pattern or record) and is composed of one or more elements (columns), called attributes (or variables).

In Rulex an attribute is uniquely identified by its name and is defined in the following way:

it belongs to a type
it has a specific role
it may or may not be used in the final data analysis

Attribute types

Attribute type	Definition	Examples of valid attributes

Attribute type	Definition	Examples of valid attributes
Nominal	An attribute with no intrinsic ordering	a color, the job of a person, a product code
Integer	A positive or negative integer	the age of a person or the answer to a questionnaire
Continuous	An intrinsically quantitative variable	the measurement of a physical quantity, the price of specific goods
Date	A date in a valid format The date format summarizes in a single field 4 quantities: the year, the month, the day, the date.	1492/10/12, 12/10/1492, 1492-10-12, 12-10-1492, 1492/Oct/12, 12/Oct/1492, 1492-Oct-12 and 12-Oct-1492
Time	A time in a valid format. The time resolution is milliseconds.	17:27:35, 17:27:35.12, 5:27:35 PM, 17:27, 5:27 PM
Datetime	A combined date and time in a valid format The datetime resolution is seconds.	date time, or dateTtime.
Month	A month in a valid format	1492/10, 10/1492, 1492-10, 10-1492, 1492/Oct, 1492-Oct, Oct/1492 and Oct-1492.
Week	A week in a valid format. International week numbering conventions are used, therefore 2014/12/30, for example, belongs to the first week of 2015.	1492/W41, W41/1492, 1492-W41, W41-1492
Quarter	A period of three months in a valid format Notice that: Q1 starts on January, 1st and ends on March, 31st, Q2 starts on April, 1st and ends on June, 30th and so on…	1492/Q3, Q3/1492, 1492-Q3, Q3-1492

Any string of printable ASCII characters, not including backslashes ‘’ or double quotation marks ‘”’, can be used for the name of any item or for the value of any attribute. Strings are memorized and shown in their original form but are always treated in a case insensitive way; consequently Rulex considers “People”, “people”, and “PEOPLE” as the same string.
Only some statistical and machine learning algorithms, such as logic learning machines, and hierarchical basket analysis, are able to deal with nominal attributes; other operations transform nominal attributes into discrete attributes. Consequently a fictitious ordering is used for the values of those attributes that may affect the outcome of the results.

Attribute roles

Each attribute of the dataset may assume one of the following roles:

Role	Definition

Role	Definition
Input	An input variable in a supervised learning problem
Output	A target variable of a supervised learning problem. When its type is nominal we are facing a classification problem, if it is discrete or continuous it a regression problem.
Profile	The attribute to be employed to measure similarities in an unsupervised learning problem.
Weight	The variable that provides a measure of relevance for each example in the dataset.
Cluster Id	A nominal attribute containing the cluster assignment for each pattern in an unsupervised learning problem. This role can also be used to provide the clustering technique with an initial assignment chosen by the user.
No Role	Variables that do not assume a specific role in the current analysis.

Attributes used for data analysis

Attributes are also characterized by a Boolean property, which defines whether or not the attribute will be used in the data analysis:

Ignore: if true, the attribute is not considered in the analysis.
Label: if true, the attribute is considered as a unique identifier of the pattern. This tag is used by the label clustering and projection clustering tasks.

Some algorithms implemented in Rulex cannot manage missing values in the data table. For this reason each attribute is also characterized by a value for missing that replaces missing record in the dataset.