Data set

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For IBM mainframe term for a file, see Data set (IBM mainframe). For the telecommunications interface device, see Modem.

A data set (or dataset) is a collection of data.

Most commonly a data set corresponds to the contents of a single database table, or a single statistical data matrix, where every column of the table represents a particular variable, and each row corresponds to a given member 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. The data set may comprise data for one or more members, corresponding to the number of rows.

The term data set may also be used more loosely, to refer to the data in a collection of closely related tables, corresponding to a particular experiment or event. An example of this type is the data sets collected by space agencies performing experiments with instruments aboard space probes.

In the open data discipline 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 datasets.[1] In this field other definitions have been proposed [2] but currently there is not an official one. Some other issues (real-time data sources,[3] non-relational datasets, etc) increases the difficult to reach a consensus about it.

History[edit]

Historically, the term originated in the mainframe field, where it had a well-defined meaning, very close to the contemporary computer file.[citation needed].

Properties[edit]

Several characteristics define a data set's 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.[4]

The values may be numbers, such as real numbers or integers, for example representing a person's height in centimeters, but may also be nominal data (i.e., not consisting of numerical values), for example representing a person's 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.[5]

Classic data sets[edit]

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

See also[edit]

Notes[edit]

  1. ^ "European open data portal". European open data poral. European commission. 17-08-2016. Retrieved 2016-08-17.  Check date values in: |date= (help)
  2. ^ "Dataset definition – MELODA". www.meloda.org. Retrieved 2016-08-17. 
  3. ^ Atz, U (2014). "The tau of data: A new metric to assess the timeliness of data in catalogues" (PDF). CEDEM 2014 Proceedings. Retrieved 2016-08-17. 
  4. ^ Jan M. Żytkow, Jan Rauch (1999). Principles of data mining and knowledge discovery. ISBN 978-3-540-66490-1. 
  5. ^ United Nations Statistical Commission; United Nations Economic Commission for Europe (2007). Statistical Data Editing: Impact on Data Quality: Volume 3 of Statistical Data Editing, Conference of European Statisticians Statistical standards and studies. United Nations Publications. p. 20. ISBN 9211169526. Retrieved 19 July 2015. 
  6. ^ Fisher, R.A. (1936). "The Use of Multiple Measurements in Taxonomic Problems" (PDF). Annals of Eugenics. 7: 179–188. doi:10.1111/j.1469-1809.1936.tb02137.x. 

External links[edit]