Machine LEARNING-III. Linear Algebra Review (Week 1, Optional)

Machine learning machines Learning-andrew NG Courses Study notes

Introduction to matrices and vectors and their representations

What is matrices matrix

Matrix is just another-a-saying, is a 2D or a, and a dimensional array.
dimensionof the matrix is going to being written as the number of the row times the number of columns in the matrix.
Written out as R4 by 2 or concretely, what people would sometimes say this matrix is a element of the set R 4 by 2.
matrix elements, (entries of matrix) the numbers inside the matrix.

The matrix gets you a-letting you quickly organize, index and access lots of data.

What is vectors vector
A vector turns out is a special case of a matrix. A vector is a matrix which has the only 1 column so you have an N x 1 matrix. {Vectors in this course are column vector}
Dimension: If has N equals four elements here.so We also call this is a four dimensional vector, just means This was a vector with four elements, with four numbers in it.
Refer to this as a vector in the set R4.

notation the canonical representation of a symbol:

Throughout the rest of these videos on linear algebra review, I'll be the using one index vectors. Most vector subscripts in the course start from 1.
When talking on machine learning applications, sometimes explicitly say if we need to switch to, when we need to use The zero index vectors as well. Discussion of machine learning applications will be converted to subscript starting from 0.

Finally, by Convention,use upper case to refer to matrices. So we ' re going-letters like a, B, c.and usually we'll use Lowercase,like A, B, X, y,to refer to either numb Ers,or just raw numbers or scalars or to vectors.

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Machine LEARNING-III. Linear Algebra Review (Week 1, Optional)