What is Vector?


What are the vectors here? [1,2,3] is the first vector and [4,5,6] is the seond vector?
[1,4] is the first, [2,5] is the second vector and the third one is [3,6]? Which one is true?

In Linear Algebra a vector is a nx1 matrix! Or better say its a column of the coordinates of a single point in a n-dimensional space!

The array you show is a 2 x 3 matrix. That is a matrix with 2 rows and 3 columns. So it all just depends on how you look at it. It has two 1 x 3 vectors as its rows and it has three 2 x 1 vectors as its columns.


Note that the data in the matrix an be organized as columns or rows. There is little standardization in this regard. You are likely to see both orientations used, even within a specific course.

Generally, in the Machine Learning Specialization, [1,2,3] is the first sample vector, and [1, 4] is the first feature vector.

@Shahbaz_Khalilli, if you were specifically questioning the meaning of “vector” in a particular lecture, I recommend you to share the lecture’s name and the timemark at which “vector” is mentioned, then we can give you a more specific answer.


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