Zhentiw - 博客园

2020年8月16日

摘要： 0 mertix doesn't have inverse. Only square materix (mxm) has inverse Tanspose: % Initialize matrix A A = [1,2,0;0,5,6;7,0,9] % Transpose A A_trans = A 阅读全文

posted @ 2020-08-16 21:04 Zhentiw 阅读(227) 评论(0) 推荐(0)

[Linear Algebra] Matrix-Matrix Multiplication

摘要： The whole idea is to conver matrix-matrix multiplication to matrix-vector multiplication. Not commutative: Identity matrix: % Initialize random matric 阅读全文

posted @ 2020-08-16 20:42 Zhentiw 阅读(227) 评论(0) 推荐(0)

2020年8月15日

[Linear Algebra] Matrix Vector Multiplication

摘要： For example the predicting house pirces example, we can code it in one line for materix vector multiplication. The tip is conver size to a m*2 matrix, 阅读全文

posted @ 2020-08-15 20:52 Zhentiw 阅读(185) 评论(0) 推荐(0)

[Linear Algebra] Matrices and Vectors

摘要： Matrices are 2-dimensional arrays: It's a 4*2 matrix 1 column's matrice is called Vector; % The ; denotes we are going back to a new row. A = [1, 2, 3 阅读全文

posted @ 2020-08-15 20:21 Zhentiw 阅读(130) 评论(0) 推荐(0)

2020年8月13日

[XState] Invoke with callback

摘要： Invoke not only able to return a promise, but also a callback function with 'sendBack' & 'receive' callbacks invoke: { // nested state with id referen 阅读全文

posted @ 2020-08-13 15:56 Zhentiw 阅读(270) 评论(0) 推荐(0)

2020年8月12日

[PostgresSQL] Install and start the service

摘要： Install: brew install postgresql Start: brew services start postgresql psql postgres Create a table: $ postgres=# create table Users ( $ postgres(# cr 阅读全文

posted @ 2020-08-12 15:40 Zhentiw 阅读(146) 评论(0) 推荐(0)

[Node.js] Serve a random static file with Express

摘要： To create a virtual path prefix (where the path does not actually exist in the file system) for files that are served by the express.static function, 阅读全文

posted @ 2020-08-12 02:50 Zhentiw 阅读(108) 评论(0) 推荐(0)

[React] Display Computed Data Using Recoil Selectors in React

摘要： In this lesson, we're going to show how RecoilJS selectors are used to display computed data in React. While atoms are the go-to state objects in Reco 阅读全文

posted @ 2020-08-12 02:40 Zhentiw 阅读(248) 评论(0) 推荐(0)

[Javascript] 4 ways to remove duplicates elements from an array with Javascript

摘要： Remove duplicates elements from an array is a common array task Javascript offers different alternatives to accomplish it. You can use a mix of method 阅读全文

posted @ 2020-08-12 02:34 Zhentiw 阅读(171) 评论(0) 推荐(0)

[ML] Cost Function

摘要： We can measure the accuracy of our hypothesis function by using a cost function. This takes an average difference (actually a fancier version of an av 阅读全文

posted @ 2020-08-12 02:29 Zhentiw 阅读(152) 评论(0) 推荐(0)

Answer1215

公告