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  2. pandas (software) - Wikipedia

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

    [4]: 114 A DataFrame is a 2-dimensional data structure of rows and columns, similar to a spreadsheet, and analogous to a Python dictionary mapping column names (keys) to Series (values), with each Series sharing an index. [4]: 115 DataFrames can be concatenated together or "merged" on columns or indices in a manner similar to joins in SQL.

  3. Null (SQL) - Wikipedia

    en.wikipedia.org/wiki/Null_(SQL)

    E. F. Codd mentioned nulls as a method of representing missing data in the relational model in a 1975 paper in the FDT Bulletin of ACM-SIGMOD.Codd's paper that is most commonly cited with the semantics of Null (as adopted in SQL) is his 1979 paper in the ACM Transactions on Database Systems, in which he also introduced his Relational Model/Tasmania, although much of the other proposals from ...

  4. NaN - Wikipedia

    en.wikipedia.org/wiki/NaN

    For the decimal formats, the usual encoding of unsigned integers is used. If an operation has a single NaN input and propagates it to the output, the result NaN's payload should be that of the input NaN (this is not always possible for binary formats when the signaling/quiet state is encoded by an is_signaling flag, as explained above). If ...

  5. Panel data - Wikipedia

    en.wikipedia.org/wiki/Panel_data

    Both datasets above are structured in the long format, which is where one row holds one observation per time. Another way to structure panel data would be the wide format where one row represents one observational unit for all points in time (for the example, the wide format would have only two (first example) or three (second example) rows of ...

  6. CAPTCHA - Wikipedia

    en.wikipedia.org/wiki/Captcha

    This CAPTCHA (reCAPTCHA v1) of "smwm" obscures its message from computer interpretation by twisting the letters and adding a slight background color gradient.A CAPTCHA (/ ˈ k æ p. tʃ ə / KAP-chə) is a type of challenge–response test used in computing to determine whether the user is human in order to deter bot attacks and spam.

  7. Nan's Christmas Carol - Wikipedia

    en.wikipedia.org/wiki/Nan's_Christmas_Carol

    Nan's Christmas Carol is a spin-off of The Catherine Tate Show. [1] The one-off special, based on Charles Dickens ' 1843 novella A Christmas Carol , is about Nan visited by three ghosts on Christmas night in her council flat.