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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]
Pandas is built around data structures called Series and DataFrames. Data for these collections can be imported from various file formats such as comma-separated values, JSON, Parquet, SQL database tables or queries, and Microsoft Excel. [8] A Series is a 1-dimensional data structure built on top of NumPy's array.
Thus an element in row i and column j of an array A would be accessed by double indexing (A[i][j] in typical notation). This way of emulating multi-dimensional arrays allows the creation of jagged arrays, where each row may have a different size – or, in general, where the valid range of each index depends on the values of all preceding indices.
To use column-major order in a row-major environment, or vice versa, for whatever reason, one workaround is to assign non-conventional roles to the indexes (using the first index for the column and the second index for the row), and another is to bypass language syntax by explicitly computing positions in a one-dimensional array.
Thus, if the array is seen as a function on a set of possible index combinations, it is the dimension of the space of which its domain is a discrete subset. Thus a one-dimensional array is a list of data, a two-dimensional array is a rectangle of data, [12] a three-dimensional array a block of data, etc.
From January 2008 to December 2012, if you bought shares in companies when Richard L. Armitage joined the board, and sold them when he left, you would have a -34.7 percent return on your investment, compared to a -2.8 percent return from the S&P 500.
From October 2009 to December 2012, if you bought shares in companies when Glenn A. Britt joined the board, and sold them when he left, you would have a 55.5 percent return on your investment, compared to a 38.5 percent return from the S&P 500.
For finite-dimensional real vectors in with the usual Euclidean dot product, the Gram matrix is =, where is a matrix whose columns are the vectors and is its transpose whose rows are the vectors . For complex vectors in C n {\displaystyle \mathbb {C} ^{n}} , G = V † V {\displaystyle G=V^{\dagger }V} , where V † {\displaystyle V^{\dagger ...