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  2. pandas (software) - Wikipedia

    en.wikipedia.org/wiki/Pandas_(software)

    If a Series uses the index value a for multiple data points, then s['a'] will instead return a new Series containing all matching values. [4]: 136 A DataFrame's column names are stored and implemented identically to an index. As such, a DataFrame can be thought of as having two indices: one column-based and one row-based.

  3. Map (higher-order function) - Wikipedia

    en.wikipedia.org/wiki/Map_(higher-order_function)

    The naturality axiom of such functions is automatically satisfied because it is a so-called free theorem, depending on the fact that it is parametrically polymorphic. [1] For example, reverse :: List a -> List a, which reverses a list, is a natural transformation, as is flattenInorder :: Tree a -> List a, which flattens a tree from left to ...

  4. NumPy - Wikipedia

    en.wikipedia.org/wiki/NumPy

    NumPy (pronounced / ˈ n ʌ m p aɪ / NUM-py) is a library for the Python programming language, adding support for large, multi-dimensional arrays and matrices, along with a large collection of high-level mathematical functions to operate on these arrays. [3]

  5. Pivot table - Wikipedia

    en.wikipedia.org/wiki/Pivot_table

    Column labels are used to apply a filter to one or more columns that have to be shown in the pivot table. For instance if the "Salesperson" field is dragged to this area, then the table constructed will have values from the column "Sales Person", i.e., one will have a number of columns equal to the number of "Salesperson". There will also be ...

  6. Data transformation (computing) - Wikipedia

    en.wikipedia.org/wiki/Data_transformation...

    [1] [2] [7] The people who need to use the data (e.g. business users) do not play a direct role in the data transformation process. [ 9 ] Typically, users hand over the data transformation task to developers who have the necessary coding or technical skills to define the transformations and execute them on the data.

  7. Non-negative matrix factorization - Wikipedia

    en.wikipedia.org/wiki/Non-negative_matrix...

    For example, if V is an m × n matrix, W is an m × p matrix, and H is a p × n matrix then p can be significantly less than both m and n. Here is an example based on a text-mining application: Let the input matrix (the matrix to be factored) be V with 10000 rows and 500 columns where words are in rows and documents are in columns. That is, we ...

  8. Inverted index - Wikipedia

    en.wikipedia.org/wiki/Inverted_index

    The purpose of an inverted index is to allow fast full-text searches, at a cost of increased processing when a document is added to the database. [2] The inverted file may be the database file itself, rather than its index. It is the most popular data structure used in document retrieval systems, [3] used on a large scale for example in search ...

  9. Vantage-point tree - Wikipedia

    en.wikipedia.org/wiki/Vantage-point_tree

    The way a vantage-point tree stores data can be represented by a circle. [6] First, understand that each node of this tree contains an input point and a radius. All the left children of a given node are the points inside the circle and all the right children of a given node are outside of the circle.