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  2. Permutation matrix - Wikipedia

    en.wikipedia.org/wiki/Permutation_matrix

    Multiplying a matrix M by either or on either the left or the right will permute either the rows or columns of M by either π or π −1.The details are a bit tricky. To begin with, when we permute the entries of a vector (, …,) by some permutation π, we move the entry of the input vector into the () slot of the output vector.

  3. pandas (software) - Wikipedia

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

    Pandas (styled as pandas) is a software library written for the Python programming language for data manipulation and analysis. In particular, it offers data structures and operations for manipulating numerical tables and time series .

  4. Unique key - Wikipedia

    en.wikipedia.org/wiki/Unique_key

    In a relational database, a candidate key uniquely identifies each row of data values in a database table. A candidate key comprises a single column or a set of columns in a single database table. No two distinct rows or data records in a database table can have the same data value (or combination of data values) in those candidate key columns ...

  5. Count-distinct problem - Wikipedia

    en.wikipedia.org/wiki/Count-distinct_problem

    In computer science, the count-distinct problem [1] (also known in applied mathematics as the cardinality estimation problem) is the problem of finding the number of distinct elements in a data stream with repeated elements. This is a well-known problem with numerous applications.

  6. Pivot table - Wikipedia

    en.wikipedia.org/wiki/Pivot_table

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

  7. Table (database) - Wikipedia

    en.wikipedia.org/wiki/Table_(database)

    In a database, a table is a collection of related data organized in table format; consisting of columns and rows.. In relational databases, and flat file databases, a table is a set of data elements (values) using a model of vertical columns (identifiable by name) and horizontal rows, the cell being the unit where a row and column intersect. [1]

  8. Today's Wordle Hint, Answer for #1257 on Wednesday, November ...

    www.aol.com/todays-wordle-hint-answer-1257...

    If you’re stuck on today’s Wordle answer, we’re here to help—but beware of spoilers for Wordle 1257 ahead. Let's start with a few hints.

  9. Gram matrix - Wikipedia

    en.wikipedia.org/wiki/Gram_matrix

    In matrix notation, = /, where has orthonormal basis vectors {} and the matrix is composed of the given column vectors {}. The matrix G − 1 / 2 {\displaystyle G^{-1/2}} is guaranteed to exist. Indeed, G {\displaystyle G} is Hermitian, and so can be decomposed as G = U D U † {\displaystyle G=UDU^{\dagger }} with U {\displaystyle U} a unitary ...