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Python Articles
Page 151 of 855
Extract the diagonal of a matrix with Einstein summation convention in Python
The Einstein summation convention provides a concise way to express array operations. The numpy.einsum() method implements this convention, allowing us to extract matrix diagonals using subscript notation like 'ii->i'. Understanding Einstein Summation for Diagonals The subscript 'ii->i' means we take elements where both indices are equal (diagonal elements) and output them as a 1D array. The repeated index i on the left indicates we want elements at positions (0, 0), (1, 1), (2, 2), etc. Basic Example Here's how to extract diagonal elements from a 4x4 matrix ? import numpy as np # ...
Read MoreGet the trace of a matrix with Einstein summation convention in Python
The einsum() method evaluates the Einstein summation convention on operands. Using the Einstein summation convention, many common multi-dimensional, linear algebraic array operations can be represented in a simple fashion. To get the trace of a matrix with Einstein summation convention, use the numpy.einsum() method. The trace is the sum of diagonal elements, which can be computed using the subscript 'ii'. Syntax numpy.einsum(subscripts, *operands) Parameters: subscripts − String specifying the subscripts for summation operands − Input arrays for the operation Basic Example Let's create a 4x4 matrix and calculate its trace ...
Read MoreReturn the angle of the complex argument in Python
To return the angle of the complex argument, use the numpy.angle() method in Python. The method returns the counterclockwise angle from the positive real axis on the complex plane in the range (-pi, pi], with dtype as numpy.float64. Syntax numpy.angle(z, deg=False) Parameters z − A complex number or sequence of complex numbers deg − Return angle in degrees if True, radians if False (default) Basic Example Let's create an array of complex numbers and find their angles − import numpy as np # Create an array of ...
Read MoreReturn the bases when first array elements are raised to powers from second array in Python
To return the bases when first array elements are raised to powers from second array, use the np.float_power() method in Python NumPy. This function raises each base in the first array to the positionally-corresponding power in the second array, returning floating-point results with a minimum precision of float64. The float_power() method differs from the standard power() function by promoting integers, float16, and float32 to floats with higher precision, ensuring the result is always inexact. This provides more usable results for negative powers and reduces overflow for positive powers. Syntax numpy.float_power(x1, x2) Parameters x1: ...
Read MoreReturn a boolean array which is True where the string element in array starts with prefix in Python
To return a boolean array which is True where string elements start with a specific prefix, use the numpy.char.startswith() method in NumPy. This function takes the input array as the first parameter and the prefix string as the second parameter. Syntax numpy.char.startswith(a, prefix, start=0, end=None) Parameters a − Input array of strings prefix − String prefix to check for start − Optional start position (default: 0) end − Optional end position (default: None) Basic Example Let's create a string array and check which elements start with the prefix 'K' − ...
Read MoreReturn the multiple vector cross product of two vectors and change the orientation of the result in Python
To compute the cross product of two vectors and change the orientation of the result, use the numpy.cross() method in Python NumPy. The method returns the vector cross product(s) with customizable axis orientation. Parameters The numpy.cross() method accepts several parameters to control vector orientation: a: Components of the first vector(s) b: Components of the second vector(s) axisa: Axis of a that defines the vector(s) (default: last axis) axisb: Axis of b that defines the vector(s) (default: last axis) axisc: Axis of c containing the cross product vector(s) (default: last axis) axis: Overrides axisa, axisb and axisc ...
Read MoreGenerate a Pseudo Vandermonde matrix of Hermite polynomial and x, y, z floating array of points in Python
To generate a pseudo Vandermonde matrix of the Hermite polynomial and x, y, z sample points, use the hermite.hermvander3d() method in NumPy. This method returns the pseudo-Vandermonde matrix where the parameter x, y, z are arrays of point coordinates, all of the same shape. The deg parameter is a list of maximum degrees of the form [x_deg, y_deg, z_deg]. Syntax The basic syntax is ? hermite.hermvander3d(x, y, z, deg) Parameters x, y, z ? Arrays of point coordinates, all of the same shape deg ? List of maximum degrees in the form ...
Read MoreEvaluate a 2-D polynomial on the Cartesian product of x and y with 1d array of coefficient in Python
To evaluate a 2-D polynomial on the Cartesian product of x and y, use the numpy.polynomial.polynomial.polygrid2d() method in Python. This function returns the values of the two-dimensional polynomial at points in the Cartesian product of x and y arrays. Syntax numpy.polynomial.polynomial.polygrid2d(x, y, c) Parameters The function accepts three parameters: x, y: One-dimensional arrays of coordinates. If x or y is a list or tuple, it is first converted to an ndarray c: Array of coefficients ordered so that coefficients for terms of degree i, j are contained in c[i, j]. If c ...
Read MoreGenerate a pseudo Vandermonde matrix of Chebyshev polynomial and x, y, z floating array of points in Python
To generate a pseudo Vandermonde matrix of the Chebyshev polynomial and x, y, z sample points, use the chebyshev.chebvander3d() function in Python NumPy. The method returns the pseudo-Vandermonde matrix of degrees deg and sample points (x, y, z). The parameters x, y, z are arrays of point coordinates, all of the same shape. The dtypes will be converted to either float64 or complex128 depending on whether any of the elements are complex. Scalars are converted to 1-D arrays. The parameter deg is a list of maximum degrees of the form [x_deg, y_deg, z_deg]. Syntax numpy.polynomial.chebyshev.chebvander3d(x, y, ...
Read MoreEvaluate a 2-D polynomial on the Cartesian product of x and y with 3d array of coefficient in Python
To evaluate a 2-D polynomial on the Cartesian product of x and y, use the polynomial.polygrid2d(x, y, c) method in Python. The method returns the values of the two-dimensional polynomial at points in the Cartesian product of x and y. The first parameter, x and y, are the coordinate arrays evaluated at points in the Cartesian product. If x or y is a list or tuple, it is first converted to an ndarray. The second parameter, c, is an array of coefficients where coefficients for terms of degree i, j are contained in c[i, j]. If c has dimension ...
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