Pratique du Shadowing: Ridge vs Lasso Regression, Visualized!!! - Apprendre l'anglais à l'oral avec la vidéo

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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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Vocabulaire et conseils d’expression pour cette leçon

Cette leçon d’expression orale s’appuie sur la vidéo « Ridge vs Lasso Regression, Visualized!!! ». Les mots qui reviennent le plus souvent : slope, penalty, lambda, equal, zero. Cette vidéo contient 86 phrases et 1111 mots à répéter en shadowing. La partie parlée dure 9:04. Le locuteur parle à un rythme régulier d’environ 122 mots par minute, confortable pour le shadowing. Seuls 70 % des mots font partie des 3 000 mots les plus courants en anglais, le vocabulaire est donc exigeant.

Vocabulaire clé de cette vidéo

15 mots de la vidéo à retenir, avec leur prononciation et leur sens :

MotPrononciationSens
slope nom/sloʊp/pente
penalty nom/ˈpɛn.əl.ti/penalisation
residual adjectif/ɹɪˈzɪd͡ʒ.u.əl/résiduel
optimal adjectif/ˈɑptɪməl/optimal
thick adjectif/θɪk/épais, gros
ridge nom/ɹɪd͡ʒ/crête
horizontal adjectif/ˌhoɹəˈzɑn.təl/horizontal
calculate verbe/ˈkælkjʊleɪt/calculer
graph nom/ɡɹæf/graphique
curve nom/kɚv/courbe
purple nom/ˈpɝ.pl̩/violet, pourpre
plug nom/plʌɡ/fiche
compare verbe/kəmˈpɛɚ/comparer
versus/ˈvɝsəs/contre, face à
quest nom/kwɛst/quête

Les verbes à particule que vous entendrez

MotSens
check out verbemater, regarder
end up verbese terminer, se finir

La grammaire de cette vidéo

Les structures que le locuteur utilise le plus, avec les mots exacts de la vidéo :

StructureDans la vidéo
Voix passive be + participe passé — l’accent est mis sur ce qui arrive, pas sur qui le faitbe visualized · should be called · are left
Present perfect have/has + participe passé — une action passée qui compte encore maintenanthas shrunk · We've made

Prononciation à surveiller

Le locuteur utilise 8 contractions et formes réduites, comme we'll, we're, I'd. Prononcez-les sous leur forme courte, telles que vous les entendez.

  • Les sons « sh » et « zh »: equation /ɪˈkweɪ.ʒən/, contrast /kənˈt(ʃ)ɹæst/, measurement /ˈmɛʒ.ə.mənt/, regression /ɹiːˈɡɹɛʃ.ən/, visualize /ˈvɪʒuəˌlaɪz/
  • Mots longs — placez bien l’accent: residual /ɹɪˈzɪd͡ʒ.u.əl/, horizontal /ˌhoɹəˈzɑn.təl/, parabola /pəˈɹæb.ə.lə/

Les sons difficiles pour les francophones :

  • /tʃ/ et /dʒ/ — à ne pas adoucir en « ch » et « j »: residual /ɹɪˈzɪd͡ʒ.u.əl/, ridge /ɹɪd͡ʒ/
  • /r/ anglais — langue recourbée, sans frotter la gorge: residual /ɹɪˈzɪd͡ʒ.u.əl/, ridge /ɹɪd͡ʒ/, horizontal /ˌhoɹəˈzɑn.təl/, graph /ɡɹæf/, predict /pɹɪˈdɪkt/

Comment s’entraîner avec cette vidéo

  1. Écoutez la vidéo en entier une fois sans parler et notez les mots que vous ne connaissez pas.
  2. Répétez phrase par phrase à vitesse normale, en reprenant chacune jusqu’à ce que votre rythme corresponde à celui du locuteur.
  3. Enregistrez-vous et comparez avec l’original, en faisant attention à des mots comme slope, penalty, residual.

Qu'est-ce que la technique du Shadowing ?

Le Shadowing est une technique d'apprentissage des langues fondée sur la science, développée à l'origine pour la formation des interprètes professionnels. Le principe est simple mais puissant : vous écoutez de l'anglais natif et le répétez immédiatement à voix haute — comme une ombre suivant le locuteur avec un décalage de 1 à 2 secondes. Les recherches montrent une amélioration significative de la précision de la prononciation, de l'intonation, du rythme, des liaisons, de la compréhension orale et de la fluidité.

Technique du shadowing : lire le guide complet étape par étape →