Linear Algebra - NumPy Part 1
List of the linear algebra concepts that are required for data science:
- Vectors and matrices: Vectors and matrices are the basic objects of linear algebra. They are used to represent data and to perform mathematical operations on data.
- Linear transformations: Linear transformations are functions that map vectors to vectors. They are used to represent relationships between data.
- Eigenvalues and eigenvectors: Eigenvalues and eigenvectors are important concepts in linear algebra. They are used to analyze the behavior of linear transformations.
- Singular value decomposition (SVD): SVD is a powerful tool for data analysis. It can be used to decompose matrices into their constituent parts.
- Principal component analysis (PCA): PCA is a dimensionality reduction technique. It can be used to reduce the number of features in a dataset without losing too much information.
- Least squares: Least squares is a method for fitting a line or curve to a set of data points. It is used in regression analysis.
- Logistic regression: Logistic regression is a statistical model that is used to predict the probability of an event. It is used in classification problems.
- Support vector machines (SVM): SVM is a machine learning algorithm that is used for classification and regression tasks. It works by finding the hyperplane that best separates the data points.
here are some NumPy examples for vectors and matrices:
- Creating a vector: A vector can be created using the
np.array()
function. Thenp.array()
function takes a list of numbers as input and creates a NumPy array with those numbers.
import numpy as np
vector = np.array([1, 2, 3])
In this example, the vector
variable is a NumPy array with 3 elements, all of which are equal to 1.
- Creating a matrix: A matrix can be created using the
np.array()
function. Thenp.array()
function takes a list of lists as input and creates a NumPy array with those lists.
import numpy as np
matrix = np.array([[1, 2, 3], [4, 5, 6]])
In this example, the matrix
variable is a NumPy array with 2 rows and 3 columns. The first row of the matrix is equal to [1, 2, 3] and the second row of the matrix is equal to [4, 5, 6].
- Indexing a vector or matrix: A vector or matrix can be indexed using integers. The index refers to the element of the vector or matrix that you want to access.
import numpy as np
vector = np.array([1, 2, 3])
first_element = vector[0]
In this example, the first_element
variable is the first element of the vector
variable, which is equal to 1.
- Slicing a vector or matrix: A vector or matrix can be sliced using slices. A slice refers to a subarray of the vector or matrix.
import numpy as np
matrix = np.array([[1, 2, 3], [4, 5, 6]])
first_row = matrix[0:1, :]
In this example, the first_row
variable is a subarray of the matrix
variable that contains the first row of the matrix.
- Adding vectors and matrices: Vectors and matrices can be added together using the
+
operator.
import numpy as np
vector1 = np.array([1, 2, 3])
vector2 = np.array([4, 5, 6])
added_vector = vector1 + vector2
In this example, the added_vector
variable is a new vector that is the sum of vector1
and vector2
.
- Multiplying vectors and matrices: Vectors and matrices can be multiplied together using the
*
operator.
import numpy as np
matrix1 = np.array([[1, 2], [3, 4]])
matrix2 = np.array([[5, 6], [7, 8]])
multiplied_matrix = matrix1 * matrix2
In this example, the multiplied_matrix
variable is a new matrix that is the product of matrix1
and matrix2
.
These are just a few examples of NumPy operations that can be performed on vectors and matrices. There are many other operations that can be performed, depending on the specific needs of the application.
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