Zhentiw - 博客园

2020年8月31日

[Prostgres] Select Grouped and Aggregated Data with SQL

摘要： Another powerful SQL skill is understanding how to group rows together by column values. Once the data is grouped together, it can be difficult to und 阅读全文

posted @ 2020-08-31 23:53 Zhentiw 阅读(131) 评论(0) 推荐(0)

[Machine Learning] Regularization Ex

摘要： If lamda is large then theta should be small in order to minize the cost function. Too large lamda, cause underfitting the data. 阅读全文

posted @ 2020-08-31 02:10 Zhentiw 阅读(142) 评论(0) 推荐(0)

[Machine Learning] Solve overfitting, Regularization

摘要： If we have overfitting from our hypothesis function, we can reduce the weight that some of the terms in our function carry by increasing their cost. S 阅读全文

posted @ 2020-08-31 01:48 Zhentiw 阅读(209) 评论(0) 推荐(0)

[Machine Learning] Logistic Regression Ex

摘要：阅读全文

posted @ 2020-08-31 01:33 Zhentiw 阅读(89) 评论(0) 推荐(0)

2020年8月28日

[Postgres] Keep Data Integrity with Constraints

摘要： If the data in your tables do not have integrity, meaning there are missing rows, incorrect values, or duplicate rows, your table is not worth much. D 阅读全文

posted @ 2020-08-28 19:30 Zhentiw 阅读(163) 评论(0) 推荐(0)

[Postgres] Removing Data with SQL Delete, Truncate, and Drop

摘要： Delete: delete from Users where last_name = 'clark'; If you wanted to delete everything in our table, I mentioned you could just use the delete comman 阅读全文

posted @ 2020-08-28 19:22 Zhentiw 阅读(150) 评论(0) 推荐(0)

[Postgres] Using uuid-ossp extenstion

摘要： PostgreSQL allows you store and compare UUID values but it does not include functions for generating the UUID values in its core. Instead, it relies o 阅读全文

posted @ 2020-08-28 18:41 Zhentiw 阅读(165) 评论(0) 推荐(0)

[Machine Learning] Simplified Cost Function and Gradient Descent

摘要： We can compress our cost function's two conditional cases into one case: We can fully write out our entire cost function as follows: A vectorized impl 阅读全文

posted @ 2020-08-28 04:07 Zhentiw 阅读(156) 评论(0) 推荐(0)

2020年8月27日

[Javascript] Wrap Arrays with Proxy

摘要： In contrast to other built-ins, Arrays can be wrapped transparently: const p = new Proxy(new Array(), {}); p.push('a'); assert.equal(p.length, 1); p.l 阅读全文

posted @ 2020-08-27 02:52 Zhentiw 阅读(164) 评论(0) 推荐(0)

[Javascript] Wrap a Javascript Built-in constructor with Proxy

摘要： Instances of most built-in constructors also use a mechanism that is not intercepted by Proxies. They therefore can’t be wrapped transparently, either 阅读全文

posted @ 2020-08-27 02:50 Zhentiw 阅读(158) 评论(0) 推荐(0)

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