Pengfei Luo
153 followers
153 followers
Pengfei's posts
Post has shared content
Determining the optimal number of clusters: 3 must known methods

Partitioning methods, such as k-means clustering require also the users to specify the number of clusters to be generated.

One fundamental question is: How to choose the right number of expected clusters (k)?

In this article, we’ll describe different methods for determining the optimal number of clusters for k-means, PAM and hierarchical clustering . These methods include direct methods and statistical testing approaches.

http://www.sthda.com/english/wiki/determining-the-optimal-number-of-clusters-3-must-known-methods-unsupervised-machine-learning﻿
Post has attachment
Post has shared content

【阿波罗新闻网 2015-08-26 讯】

01你到底“在”哪里

At是一个点。

On是一个面。

In是一个空间。

I’ll meet you at the office.

(我们在办公室见。)指地点。

I’m in my office.

(我正在工作。)

In不只是在办公室，而是做着在那个空间里应该发生的事;好比in school是求学，in class是上课，in the office是办公。

(请打电话到我办公室给我。)

02 at< on< in介系词的时间感

At表示特定的时间点。

I got up at7:00 this morning.(我今天早上7点起床。)

The miracle happened at that moment.(奇迹在那一刻发生了。)

On表示特定的日子或日期。

His birthday is on the fourth of August.(他的生日在8月4日)

We are going to the party on Halloween.(万圣节当天我们会去参加派对。)

In表示特定较长的时间。

My uncle is going to retire in2015.(我舅舅2015就要退休了。)

She started the job in August.(她在8月的时候就开始做这工作了。)

03培养对介系词的感觉

(1) to/for

To是“朝着目标去”的感觉，目标明确，一定会到);for是“朝着一个方向去”的感觉，是一个大方向，并没有说一定会到。例如：Give the proposal to me.(将那计划书交给我。)“给(give)”这个动作必须要作用在"me"身上才算完成，所以用to。

(2) with/by

With是“伴随着/在旁边”的感觉，by则是“靠…过去”的感觉。例如：

I will go with May.(我会和May一起去。)

I opened the door with a key.(我“用”一把钥匙开那扇门。)或者

I went there by train.(我搭火车到那里。)

“靠…过去”是透过train这种交通工具抵达，不能用I went there"with" train，这样会变成“使用(手拿着)”train到那儿。

(3) of

The table is made of glass.(桌子是由玻璃制成。)桌子是从玻璃中“分离出来的”。

04 Up让句子更有力

(1)当我听到这事时，我简直不敢相信我的耳朵。

I couldn’t believe my ears when I heard this.

=> I couldn’t believe my ears at this.

(2)她死后留下6个孩子。

She left six children after she died.

=> She left six children behind her.

(3)如果需要帮助，打给我，号码是2721-5033。

If you need help, just ring me. My telephone number is2721-5033.

=> If you need help, just call me at2721-5033.

(4)我们举杯庆祝他的成功。

We raise a toast to congratulate him on his great success.

=> We raise a toast to his great success.

(5)这段文章生词太多，我要理解真是太难了。

There are so many new words in this passage, so it is hard for me to understand.

=> With so many new words, this passage is beyond me.

(6)他因为30票之差输了竞选。

He lost the election because of30 votes.

=> He lost the election by30 votes.

(7)证据对他不利。

The evidence is not good for him.

=> The evidence is against him.

(8)我可以帮你完成这个专案。

(9)我买单。

I’ll pay the bill.

=> It’s on me.

Post has shared content
The film was banned in China not long before it was to be released in Chinese cinemas, I think the government just changed its mind and thought the film is too negative about the society. It is indeed a dark one. All figures are from grassroots of the society suffering from different unbearable conditions. Not a fun one, but worth watching and quite reflective on human conditions in a fast changing society. All the four stories are highly contextualized in different recent social issues in China: coalmine accidents, collusion of politics and business, increasing corruption and violence, suicides migrant worker and deprivation of labor rights in manufacturing industries, sex and crime, etc.﻿
Post has shared content
How do touch screens work? Watch this #NatandLo episode to find out → g.co/go/NLphone﻿
Post has attachment