# ⓘ Data set. A data set is a collection of data. In the case of tabular data, a data set corresponds to one or more database tables, where every column of a table ..

## ⓘ Data set

A data set is a collection of data. In the case of tabular data, a data set corresponds to one or more database tables, where every column of a table represents a particular variable, and each row corresponds to a given record of the data set in question. The data set lists values for each of the variables, such as height and weight of an object, for each member of the data set. Each value is known as a datum. Data sets can also consist of a collection of documents or files.

In the open data discipline, data set is the unit to measure the information released in a public open data repository. The European Open Data portal aggregates more than half a million data sets. In this field other definitions have been proposed, but currently there is not an official one. Some other issues increases the difficulty to reach a consensus about it.

## 1. Properties

Several characteristics define a data sets structure and properties. These include the number and types of the attributes or variables, and various statistical measures applicable to them, such as standard deviation and kurtosis.

The values may be numbers, such as real numbers or integers, for example representing a persons height in centimeters, but may also be nominal data i.e., not consisting of numerical values, for example representing a persons ethnicity. More generally, values may be of any of the kinds described as a level of measurement. For each variable, the values are normally all of the same kind. However, there may also be missing values, which must be indicated in some way.

In statistics, data sets usually come from actual observations obtained by sampling a statistical population, and each row corresponds to the observations on one element of that population. Data sets may further be generated by algorithms for the purpose of testing certain kinds of software. Some modern statistical analysis software such as SPSS still present their data in the classical data set fashion. If data is missing or suspicious an imputation method may be used to complete a data set.

## 2. Classic data sets

Several classic data sets have been used extensively in the statistical literature:

• Bayesian Data Analysis – Data used in the book are provided on-line by Andrew Gelman, one of the books authors.
• Iris flower data set – Multivariate data set introduced by Ronald Fisher 1936.
• MNIST database – Images of handwritten digits commonly used to test classification, clustering, and image processing algorithms
• The Bupa liver data – Used in several papers in the machine learning data mining literature.
• Robust statistics – Data sets used in Robust Regression and Outlier Detection Rousseeuw and Leroy, 1986. Provided on-line at the University of Cologne.
• Anscombes quartet – Small data set illustrating the importance of graphing the data to avoid statistical fallacies
• Extreme values – Data used in the book, An Introduction to the Statistical Modeling of Extreme Values are a snapshot of the data as it was provided on-line by Stuart Coles, the books author.
• Categorical data analysis – Data sets used in the book, An Introduction to Categorical Data Analysis.
• Time series – Data used in Chatfields book, The Analysis of Time Series, are provided on-line by StatLib.

• In computer science, a set is an abstract data type that can store unique values, without any particular order. It is a computer implementation of the
• The Iris flower data set or Fisher s Iris data set is a multivariate data set introduced by the British statistician and biologist Ronald Fisher in his
• A Key Sequenced Data Set KSDS is a type of data set used by the IBM VSAM computer data storage system. Each record in a KSDS data file is embedded with
• In the context of IBM mainframe computers, a data set IBM preferred or dataset is a computer file having a record organization. Use of this term began
• science, a disjoint - set data structure also called a union find data structure or merge find set is a data structure that tracks a set of elements partitioned
• science a level set data structure is designed to represent discretely sampled dynamic level sets functions. A common use of this form of data structure is
• three data sets are commonly used in different stages of the creation of the model. The model is initially fit on a training dataset, that is a set of examples
• Data cleansing or data cleaning is the process of detecting and correcting or removing corrupt or inaccurate records from a record set table, or database
• Data mining is the process of discovering patterns in large data sets involving methods at the intersection of machine learning, statistics, and database
• into a unified fused data set which includes all of the data points and time steps from the input data sets The fused data set is different from a simple