《机器学习基石》第一讲心得笔记

第一讲: The Learning Problem

什么是机器学习?(Key Essence of Machine Learning)

Machine Learning: improving some performance measure with experience computed from data

也即

data $\to$ ML $\to$ improved performance measure

简单地说,机器学习就是把数据或资料“喂给”相应的算法,使得问题的某个性能衡量指标的表现更加优秀(也可以说某个skill更加熟练)。这里面涉及到三个要点(三种颜色标出),构成了能用机器学习解决的问题的三个条件:

重回hexo

虽然说ghost有后台,但是主题不合我胃口啊!!!

还是换回hexo吧,哼! (#  ̄︿ ̄)

how to get the data of a specific worksheet of one Google spreadsheet by gid

If we only want to get the data of the first worksheet of the spreadsheet, we don’t need to care about the gid in url, because the gid of this worksheet is always 0 by default. So we can just get the data of the first worksheet by the following request urls:

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https://spreadsheets.google.com/feeds/list/key/od6/private/full?alt=json
https://spreadsheets.google.com/feeds/cells/key/od6/private/full?alt=json

In the two request urls, the key (also called spreadsheet-id) is unique to each spreadsheet, which can be fetched from the url of the spreadsheet; the option alt=json is the return type of the worksheet data, which can be alt=xml as well, or you can just leave it blank.

javascript中往array中push另一个array的陷阱

先给一个例子,考察一下下面的代码输出什么。

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var arr = new Array(3);
var arr2 = new Array(3);

arr2[0] = 'A';
arr2[1] = 'B';
arr2[2] = 'C';
arr.push(arr2);

arr2[0] = 'D';
arr2[1] = 'E';
arr2[2] = 'F';
arr.push(arr2);

var arr3 = new Array;
arr3[0] = 'G';
arr3[1] = 'H';
arr3[2] = 'I';
arr.push(arr3);

document.write(arr);

对这段代码,实际上会输出

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,,,D,E,F,D,E,F,G,H,I

而不是

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D,E,F,D,E,F,G,H,I

更不是

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A,B,C,D,E,F,G,H,I