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  2. Document-term matrix - Wikipedia

    en.wikipedia.org/wiki/Document-term_matrix

    which shows which documents contain which terms and how many times they appear. Note that, unlike representing a document as just a token-count list, the document-term matrix includes all terms in the corpus (i.e. the corpus vocabulary), which is why there are zero-counts for terms in the corpus which do not also occur in a specific document.

  3. Data orientation - Wikipedia

    en.wikipedia.org/wiki/Data_orientation

    Tabular data is two dimensional — data is modeled as rows and columns. However, computer systems represent data in a linear memory model, both in-disk and in-memory. [7] [8] [9] Therefore, a table in a linear memory model requires mapping its two-dimensional scheme into a one-dimensional space.

  4. Pivot table - Wikipedia

    en.wikipedia.org/wiki/Pivot_table

    A pivot table usually consists of row, column and data (or fact) fields. In this case, the column is ship date, the row is region and the data we would like to see is (sum of) units. These fields allow several kinds of aggregations, including: sum, average, standard deviation, count, etc.

  5. Spearman's rank correlation coefficient - Wikipedia

    en.wikipedia.org/wiki/Spearman's_rank_correlation...

    Python has many different implementations of the spearman correlation statistic: it can be computed with the spearmanr function of the scipy.stats module, as well as with the DataFrame.corr(method='spearman') method from the pandas library, and the corr(x, y, method='spearman') function from the statistical package pingouin.

  6. Benford's law - Wikipedia

    en.wikipedia.org/wiki/Benford's_law

    This is an accepted version of this page This is the latest accepted revision, reviewed on 17 January 2025. Observation that in many real-life datasets, the leading digit is likely to be small For the unrelated adage, see Benford's law of controversy. The distribution of first digits, according to Benford's law. Each bar represents a digit, and the height of the bar is the percentage of ...

  7. Index of coincidence - Wikipedia

    en.wikipedia.org/wiki/Index_of_coincidence

    The products n(n − 1) count the number of combinations of n elements taken two at a time. (Actually this counts each pair twice; the extra factors of 2 occur in both numerator and denominator of the formula and thus cancel out.) Each of the n i occurrences of the i-th letter matches each of the remaining n i − 1 occurrences

  8. Counting sort - Wikipedia

    en.wikipedia.org/wiki/Counting_sort

    The initialization of the count array, and the second for loop which performs a prefix sum on the count array, each iterate at most k + 1 times and therefore take O(k) time. The other two for loops, and the initialization of the output array, each take O ( n ) time.

  9. Word2vec - Wikipedia

    en.wikipedia.org/wiki/Word2vec

    Word2vec is a group of related models that are used to produce word embeddings.These models are shallow, two-layer neural networks that are trained to reconstruct linguistic contexts of words.