跟读练习: Ridge vs Lasso Regression, Visualized!!! - 通过视频学习英语口语
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Ridge, regression versus lasso regression, which one will survive?
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StatQuest.
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Hello, I'm Josh Starmer and welcome to StatQuest.
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Today we're going to talk about ridge versus lasso regression and the differences are going to be visualized.
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Note, this StatQuest assumes that you are already familiar with ridge and lasso regression.
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If not, check out the quests.
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To show you the difference between ridge and lasso regression, we're going to use a very simple data set that consists of weight and height measurements.
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And we'll start by fitting this horizontal line to the data.
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This horizontal line represents a terrible fit.
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And we can measure how bad that fit is by calculating residuals, the difference between the observed and predicted values.
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In order to compare the horizontal line to other lines fit to the data, we will plot the sum of the squared residuals on a graph.
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The y-axis on this graph is the sum of the squared residuals,
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and the x-axis represents different slope values for the fitted line.
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In this case, the slope for the horizontal line is 0.
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Now let's increase the slope to 0.2, and calculate a new value for the sum of the squared residuals.
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Now let's increase the slope to 0.4, and calculate a new value for the sum of the squared residuals.
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We can keep plugging in new values for the slope and plotting the sum of the squared residuals,
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Or we can just plot the curve for this equation.
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We can see that the best fitting line is at the bottom of the parabola.
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In other words, when the slope equals 0.45, we get the lowest sum of the squared residuals.
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In this example, we simply calculated the sum of the squared residuals for different slopes.
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Now let's add the ridge regression penalty, aka the L2 norm.
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if you asked me, it should be called the squared penalty, since that's what it is, and, for me, way easier to remember.
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The thick blue line that we just drew represents lambda equals zero.
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This is because when lambda equals zero, the penalty is equal to zero,
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regardless of the slope, and we are left with the original sum of squared residuals.
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Now let's see what happens when we set lambda equal to 10.
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And just like before, we'll start with a horizontal line, only this time, the line is orange.
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Just like before, we can calculate the residuals.
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And we can calculate the sum of the squared residuals plus lambda times the slope squared.
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In this case, lambda equals 10.
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And the slope of the horizontal line is 0.
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So the penalty is 0.
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So we plot the sum of the squared residuals here.
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Now let's increase the slope to 0.2.
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Note, the residuals are smaller than before, so the sum of squared residuals is smaller than before.
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But now the penalty is 0.4.
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And that gives us this point on the graph.
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Now let's increase the slope to 0.4.
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And the residuals are even smaller.
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But now the penalty is 1.6.
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And that gives us this point on the graph.
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And like we did before, we can keep plugging in new values for the slope and plotting the sum of the squared residuals plus the penalty,
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or we can just plot the curve with a thick orange line that represents lambda equals 10.
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The bottom of the parabola is where the slope gives us the lowest sum of squared residuals plus penalty,
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and that corresponds to this specific line.
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And when we compare that to the optimal slope when lambda equals zero,
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we see that setting lambda equal to 10 results in a smaller optimal slope.
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Note, we can also see that when lambda equals 10, the lowest point in the parabola is closer to zero than when lambda equals zero.
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So, either way we look at it, we see that the larger value for lambda shrunk the optimal value for the slope.
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Likewise, the thick green line represents lambda equals 20.
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We see that the minimum value is closer to zero, and the optimal slope has shrunk some more.
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The purple lines represent lambda equals 40, and it shrinks the slope even more.
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In other words, as we increase lambda for the ridge regression penalty, a.k.a the L2 penalty, a.k.a the square penalty,
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The optimal slope gets closer and closer to zero, but it does not equal zero.
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Bam!
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Now let's see what happens if we use the lasso penalty, a.k.a the L1 norm, or, if you asked me,
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I'd call it the absolute value penalty.
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Unfortunately, no one asked me.
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Again, the thick blue line represents lambda equals zero, so there is no extra penalty.
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This is because when we plug lambda equals zero into the equation, the penalty becomes zero.
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And we are left with the original sum of the squared residuals.
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Note, just like before, we'll keep track of the best fitting line plus penalty in this graph on the left.
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The thick orange line represents lambda equals 10, so now we are turning on the penalty and shrinking the slope.
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When lambda equals 10, we start to see a kink in the curve where the slope is 0.
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The thick green line represents lambda equals 20, and this kink at zero is becoming more prominent.
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Lastly, the thick purple line represents lambda equals 40.
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And now the kink at zero is super obvious.
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Now the lowest point in the purple curve,
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aka the optimal slope given the absolute value penalty when lambda equals 40, is zero.
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And that means the slope of the optimal line is 0.
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And that means when lambda equals 40, we ignore weight as a variable when predicting height.
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Double bam!
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In summary, when we increase the ridge regression penalty, a.k.a the L2 penalty, a.k.a the square penalty,
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the optimal slopes shift towards zero, but we retain a nice parabola shape.
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And even when we set lambda to something crazy high like 400, we still end up with an optimal value greater than zero.
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In contrast, when we increase the lasso penalty, a.k.a the L1 penalty, a.k.a the absolute value penalty,
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The optimal value shifts towards zero, but since we have a kink at zero, zero ends up being the optimal slope.
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Bam!
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Hooray!
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We've made it to the end of another exciting StatQuest.
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If you like this StatQuest and want to see more, please subscribe.
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And if you want to support StatQuest, consider contributing to my Patreon campaign,
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becoming a channel member, buying one or two of my original songs or a t-shirt or a hoodie or just donate.
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The links are in the description below.
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All right, until next time, quest on!
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推荐视频
本课的词汇与口语要点
这节口语课以视频“Ridge vs Lasso Regression, Visualized!!!”为素材。 视频中反复出现的词有:slope, penalty, lambda, equal, zero。 这段视频共有 86 个句子、1111 个单词可供跟读。 讲话部分时长为 9:04。 说话人语速平稳,每分钟约 122 个词,很适合跟读。 只有 70% 的单词属于英语最常用的 3,000 词,词汇难度较高。
视频中的重点词汇
视频中 15 个值得学习的单词,附发音和释义:
| 单词 | 发音 | 释义 |
|---|---|---|
| slope 名词 | /sloʊp/ | 斜坡, 坡 |
| penalty 名词 | /ˈpɛn.əl.ti/ | 懲罰 /惩罚 |
| optimal 形容词 | /ˈɑptɪməl/ | 最佳的 |
| thick 形容词 | /θɪk/ | ху, 厚 |
| ridge 名词 | /ɹɪd͡ʒ/ | 背脊 |
| horizontal 形容词 | /ˌhoɹəˈzɑn.təl/ | 水平, 橫的 /横的 |
| calculate 动词 | /ˈkælkjʊleɪt/ | 計算 /计算, 算 |
| graph 名词 | /ɡɹæf/ | 圖表 /图表 |
| curve 名词 | /kɚv/ | 彎子 /弯子 |
| purple 名词 | /ˈpɝ.pl̩/ | 紫色 |
| plug 名词 | /plʌɡ/ | 插頭 /插头 |
| compare 动词 | /kəmˈpɛɚ/ | 比, 比較 /比较 |
| versus | /ˈvɝsəs/ | 對 /对 |
| quest 名词 | /kwɛst/ | 探索, 尋求 /寻求 |
| predict 动词 | /pɹɪˈdɪkt/ | 預言 /预言 |
视频中出现的短语动词
| 单词 | 释义 |
|---|---|
| check out 动词 | 退房 |
| end up 动词 | 到达 |
视频中的语法
说话人最常用的结构,并附上视频中的原话:
| 结构 | 视频中的用法 |
|---|---|
| 被动语态 be + 过去分词 — 强调发生了什么,而不是谁做的 | be visualized · should be called · are left |
| 现在完成时 have/has + 过去分词 — 过去发生但与现在仍有关联的事 | has shrunk · We've made |
需要注意的发音
说话人用了 8 次缩略和弱读形式,例如 we'll, we're, I'd。请按听到的简短形式来说。
- “sh” 和 “zh” 音: equation /ɪˈkweɪ.ʒən/, contrast /kənˈt(ʃ)ɹæst/, measurement /ˈmɛʒ.ə.mənt/, regression /ɹiːˈɡɹɛʃ.ən/, visualize /ˈvɪʒuəˌlaɪz/
- 长单词——注意重音位置: residual /ɹɪˈzɪd͡ʒ.u.əl/, horizontal /ˌhoɹəˈzɑn.təl/, parabola /pəˈɹæb.ə.lə/
中文母语者容易读错的音:
- /v/ — 不要读成 /w/,上齿轻触下唇: curve /kɚv/, versus /ˈvɝsəs/, variable [ˈvæɹ.i.ə.bl̩], observe /əbˈzɜːv/, visualize /ˈvɪʒuəˌlaɪz/
- 词尾辅音 — 要读清楚,后面不要加元音: slope /sloʊp/, thick /θɪk/, ridge /ɹɪd͡ʒ/, calculate /ˈkælkjʊleɪt/, graph /ɡɹæf/
- /r/ 和 /l/ 的区别: residual /ɹɪˈzɪd͡ʒ.u.əl/, horizontal /ˌhoɹəˈzɑn.təl/, regardless /ɹɪˈɡɑɹd.lɪs/, variable [ˈvæɹ.i.ə.bl̩], parabola /pəˈɹæb.ə.lə/
如何用这段视频练习
- 先完整听一遍视频,不要开口,记下不认识的单词。
- 用正常速度逐句跟读,每句重复到你的节奏与说话人一致为止。
- 录下自己的声音并与原声对比,特别注意 slope, penalty, optimal 这类单词。
什么是跟读法?
跟读法 (Shadowing) 是一种有科学依据的语言学习技巧,最初开发用于专业口译员的培训,并由多语言者Alexander Arguelles博士普及。这个方法简单而强大:您在听英语母语原声的同时立即大声重复——就像是一个延迟1-2秒紧跟说话者的影子。与被动听力或语法练习不同,跟读法强迫您的大脑和口腔肌肉同时处理并模仿真实的讲话模式。研究表明它能显着提高发音准确性,语调,节奏,连读,听力理解和口语流利度——使其成为雅思口语备考和真实英语交流最有效的方法之一。
















