?bootstrapping

bootstrapping發(fā)音

['bu:tstræpiŋ]

英：　　美：

bootstrapping中文意思翻譯

n. 自力更生

動(dòng)詞bootstrap的現(xiàn)在分詞形式

bootstrapping詞形變化

動(dòng)詞過(guò)去分詞: bootstrapped | 動(dòng)詞第三人稱單數(shù): bootstraps | 動(dòng)詞現(xiàn)在分詞: bootstrapping | 動(dòng)詞過(guò)去式: bootstrapped |

bootstrapping同義詞

flush | charge | the boot | bring up | iron boot | kick | thrill | strike | reboot | bang | hack | iron heel | kicking | rush | shoe | put the boot in

bootstrapping反義詞

shoe

bootstrapping常見(jiàn)例句

1 、Many kernel modules are loaded dynamically by the bootstrap system, and parameters for those modules cannot be given on the command line.───17自舉系統(tǒng)在動(dòng)態(tài)地讀取很多內(nèi)核模塊，并且這些模塊的參數(shù)不能在命令行給出。

2 、A small routine stored in ROM, called the BOOTSTRAP LOADER or IPL(Initial Program Loader),reads a spectial load routine from the diskette.───存放于ROM中的一小段稱為引導(dǎo)裝入程序或IPL（初始程序裝和程序）的常規(guī)程序從磁盤(pán)讀取一個(gè)特定的裝入程序。

3 、For classes loaded by the bootstrap class loader,───對(duì)于由bootstrap類(lèi)別載入器載入的類(lèi)別,搜索

4 、Static -! Do not set this during bootstrap! Causes binaries to be statically linked instead of dynamically?───在系統(tǒng)引導(dǎo)過(guò)程中切勿使用該參數(shù)!因?yàn)檫@將導(dǎo)致二進(jìn)制可執(zhí)行文件使用靜態(tài)連接而不是動(dòng)態(tài)連接?

5 、On the Edgeworth Expansion and the Bootstrap Approximation for a L-statistic───L一統(tǒng)計(jì)量的Edgeworth展開(kāi)和Bootstrap副近

6 、Based on genetic algorithm on optimizing the parameter of artificial neural network and nearest neighbor bootstrapping regressive model, the automatic coupling model of NNBR-ANN is obtained.───以基本遺傳算法為基礎(chǔ),優(yōu)化人工神經(jīng)網(wǎng)絡(luò)與最近鄰耦合模型的基本參數(shù),得到無(wú)參數(shù)的自適應(yīng)NNBR-ANN耦合模型。

7 、3. Now, we try to "bootstrap" our way up to L in a series of steps.───于是，用一系列的步驟，我們就可“自展”我們的方法，以接近l。

8 、bootstrap combined programming language───BCPL語(yǔ)言, 自展組合的程序語(yǔ)言

9 、Bootstrap Finance: The Art of Start-Ups by Amar V.───對(duì)人們對(duì)佛學(xué)的諸多困惑予以堅(jiān)定明確的開(kāi)釋。

10 、For example, DHCP broadcasting data increase the burden on Internet, and DHCP inherits the redundant protocol header of BOOTP (Bootstrap Protocol).───但隨著網(wǎng)絡(luò)的高速發(fā)展,DHCP的缺點(diǎn)也日益暴露,如:DHCP使用的廣播數(shù)據(jù)增加了網(wǎng)絡(luò)的負(fù)荷:DHCP本身還繼承了自舉協(xié)議(BOOTP,Bootstrap Protocol)冗長(zhǎng)的協(xié)議頭部等。

11 、As an alternative to bootstrapping, you can predeploy components by using an electronic software distribution system such as Microsoft Systems Management Server.───作為引導(dǎo)功能的一種替代選擇,可以使用諸如Microsoft Systems Management Server之類(lèi)的電子軟件分發(fā)系統(tǒng)對(duì)組件進(jìn)行預(yù)部署。

12 、Bootstrap -! Internal use only! DO NOT SET THIS FLAG YOURSELF!, Used during original system bootstrapping───僅供內(nèi)部使用,請(qǐng)勿改動(dòng)!在原始系統(tǒng)的引導(dǎo)過(guò)程中使用

13 、A New Security Bootstrap Scheme for Large Scale Wireless Sensor Networks───一種新的大規(guī)模無(wú)線傳感器網(wǎng)絡(luò)安全引導(dǎo)模式

14 、The parallel between a single individual's success and the bootstrap effort of the mass of ghetto youth is and remains too tenuous to comport with reality .───個(gè)人的成就與廣大黑人區(qū)青年依靠自己的努力取得成功之間的可比性極其微小，很不現(xiàn)實(shí)。

15 、If the parameter loader is null, the class is loaded through the bootstrap class loader.The class is initialized only if the initialize parameter is true and if it has not been initialized earlier.───如果參數(shù)loader是null，類(lèi)的加載通過(guò)引導(dǎo)類(lèi)加載器進(jìn)行，只有 initialize參數(shù)為true，并且還沒(méi)有被初始化時(shí)才初始化。

16 、The process of bringing up the operating system is called booting (originally this was bootstrapping and alluded to the process of pulling yourself up "by your bootstraps").───一臺(tái)沒(méi)有軟件運(yùn)行的電腦只是一堆發(fā)熱的電子器件。當(dāng)計(jì)算機(jī)起電啟動(dòng)開(kāi)始的第一件事情就是運(yùn)行一個(gè)叫做“操作系統(tǒng)”的特殊程序。

17 、The bootstrap partition should be the first one you create.───啟動(dòng)分區(qū)應(yīng)該是您第一個(gè)創(chuàng)建的分區(qū)。

18 、reserve flow bootstrap cycle───反流自舉式循環(huán)

19 、If you wanted to get on, you did it on your own, pulling yourself up by your bootstraps.─── 想要出人頭地 就得靠自己 用雙手打造美好的未來(lái)

20 、Regardless of whether you have taken venture capital or not, capital efficiency and bootstrapping are critical values.───不考慮你是否風(fēng)險(xiǎn)投資，資金的有效性和引導(dǎo)指令具有決定性的價(jià)值。

21 、Although it seems logical to do many things on your own (it's called bootstrapping, right?), relying on the expertise of others (and paying them when necessary) is usually a better choice.───盡管看起來(lái)很多事情由自己來(lái)做是正確的選擇（我們把它叫作步步為營(yíng)法，對(duì)吧？），但通常情況下，依靠專業(yè)人士是一個(gè)更好的選擇（必要時(shí)可以雇傭他們）。

22 、It is the abbreviated name of the device being used to bootstrap a program,for example,MDO is the boot name for device MDDO.───它是用來(lái)對(duì)程序進(jìn)行引導(dǎo)的設(shè)備的縮寫(xiě)名，例如，MDO為設(shè)備MDDO的引導(dǎo)名。

23 、A Bootstrapping Method for Automatic Semantic Pattern Acquisition───一種基于自舉原理的語(yǔ)義模式自動(dòng)獲取方法

24 、My thoughts was completely destroyed, that my individual progress could be regarded as an advance for all Negroes.The " bootstrap effort" means self-reliant effort.───它粉碎了我的個(gè)人發(fā)展可被奉為所有黑人進(jìn)步的想法。

25 、Estimation on Treasury Bond Yield Curve with Generalized Bootstrap Method───基于廣義息票剝離法的國(guó)債收益率曲線的估計(jì)

26 、The Anoka Yellow and Guangxi Yellow chicken were grouped together with a bootstrap value of 80%, but the Luxi Fighting chicken had its own branch.───安卡黃雞和廣西黃雞聚在一起；魯西斗雞獨(dú)自為一類(lèi)。

27 、In the developing world there are two reasons.One is obviously the price which is always a big issue, especially if you want to bootstrap your own IT technology.───在開(kāi)發(fā)者的世界里有兩個(gè)原因，首先，很明顯，價(jià)格總是一個(gè)大問(wèn)題，特別當(dāng)你想逐步建立起你的IT系統(tǒng)的時(shí)候。

28 、And then this branch converges with red fox with bootstrap value of 52 in UPGMA tree, 67 in NJ tree and 55 in MP tree, which is comparatively low.───之后該分支與赤狐聚成一支，自舉置信水平在UPMGA樹(shù)中為52，在NJ樹(shù)中為67，在MP樹(shù)中為55。 這一分支的自舉置信水平較低，但也均達(dá)到了50以上。

29 、The next page will discuss the Bootstrap Protocol (BOOTP).───下一頁(yè)將討論開(kāi)機(jī)啟動(dòng)協(xié)定(BOOTP)。

30 、Traditionally, the term bootstrap refers to a person who tries to stand up by pulling his own boots.───傳統(tǒng)意義的鞋帶指的是一個(gè)試圖站起來(lái)的人要先穿上自己的靴子。

31 、Pulled yourself up by your bootstraps I like that.─── 一步一步往上爬 很不錯(cuò)

32 、The advantage of making a modal application is that it's relatively simple to implement and therefore a reasonable way to bootstrap the application to function offline.───優(yōu)勢(shì):使用一個(gè)模態(tài)應(yīng)用程序的優(yōu)勢(shì)在于它的實(shí)現(xiàn)相對(duì)簡(jiǎn)單,所以它提供了一個(gè)解決應(yīng)用程序離線的合理的方法。

33 、The process of installing prerequisite components is also known as bootstrapping.───安裝系統(tǒng)必備組件的過(guò)程又稱為“引導(dǎo)”。

34 、It consists of a master bootstrap loader code (446 bytes) and four subsequent, identically structured partition records.───主引導(dǎo)記錄由三部分組成：(1)主引導(dǎo)程序；(2)四個(gè)分區(qū)表；

35 、To use a bootstrap.───使用一引導(dǎo)程序。

36 、The model is applied to forecast the annual runoff of QingTong Xia of Yellow River and compare with Artificial neural network and nearest neighbor bootstrapping regressive model.───應(yīng)用此模型對(duì)黃河青銅峽年平均流量進(jìn)行預(yù)測(cè),并與單獨(dú)的人工神經(jīng)網(wǎng)絡(luò)模型和最近鄰抽樣回歸模型預(yù)測(cè)結(jié)果進(jìn)行比較分析。

37 、The software generating system NDHD is based on the ideas of system programming languages and bootstrapping technique.───NDHD軟件自動(dòng)產(chǎn)生系統(tǒng)是一個(gè)基于系統(tǒng)程序設(shè)計(jì)語(yǔ)言和自展技術(shù)的系統(tǒng)。

38 、If the bootstrap partition is not created with the───如果啟動(dòng)分區(qū)并非

39 、If you disable bootstrapping, the application will still be installed but might not run if the prerequisites are not already installed.───如果禁用引導(dǎo),則在尚未安裝系統(tǒng)必備組件的情況下,仍將安裝應(yīng)用程序,但應(yīng)用程序可能不會(huì)運(yùn)行。

40 、A Bootstrapping Method for Acquisition of Bi-relations and Bi-relational Patterns───一種自舉的二元關(guān)系和二元關(guān)系模式獲取方法

41 、Study and Development of Bootstrap Program for PCI-based Physical Isolation Card───基于PCI的物理隔離卡自舉程序研究與開(kāi)發(fā)

42 、Community Edition is designed to bootstrap development teams and agile enterprises to quickly get started with the application development and deployment process.───Community Edition用于引導(dǎo)開(kāi)發(fā)團(tuán)隊(duì)和敏捷企業(yè)快速進(jìn)入應(yīng)用程序開(kāi)發(fā)和部署過(guò)程。

43 、Distribution Approximation in Censored Regression Model by Randomly Weighting Bootstrap───刪失回歸模型的隨機(jī)逼近

44 、THE FUNCTION OF BOOTSTRAP CAPACITYIN COMPLEMENTARY SYMMETRY CIRCUIT OF POWER AMPLIFIER───互補(bǔ)對(duì)稱功放電路中自舉電容的作用

45 、I picked myself up by my bootstraps and got to it.─── 我憑一己之力站起來(lái)走到現(xiàn)在

46 、For both Windows Installer and ClickOnce deployment, bootstrapping of the.NET Framework is enabled by default.───對(duì)于Windows Installer和ClickOnce部署,.NET Framework的引導(dǎo)功能均默認(rèn)啟用。

47 、General conditions for the success of bootstrapping models. 6002.rar (458.───8 KB)但使龍城飛將在，不教胡馬度陰山.

48 、1.To use a bootstrap loader routine.───使用引導(dǎo)裝入程序。

49 、Use angels to augment bootstrapping.───使用天使，以增加舉。

50 、Based on both the Bootstrap method and the CWT, one method is presented to construct the knowledge base of machine condition.───以此為基礎(chǔ)，論文系統(tǒng)地闡明了應(yīng)用Bootstrap方法建立設(shè)備狀態(tài)特征庫(kù)的方法。

51 、Otherwise, all their little up by your own bootstraps bullshit, it don't apply.─── 否則的話 他們那些自強(qiáng)自立的屁話 就不適用了

52 、A Robust Bootstrapping Algorithm of Speaker Models for On-Line Unsupervised Speaker Indexing───在線無(wú)監(jiān)督說(shuō)話人檢索中穩(wěn)健的模型自舉算法

53 、Without bootstrapping on themself, embedded systems always request a cross development tool chain.───嵌入式系統(tǒng)本身不具備自舉開(kāi)發(fā)能力，必須有交叉編譯開(kāi)發(fā)工具和環(huán)境才能進(jìn)行開(kāi)發(fā)。

54 、Why bootstrap? There are a couple of good reasons a company should consider bootstrapping its market entry───為什么白手起家? 這里有幾個(gè)好的原因會(huì)促使一個(gè)公司考慮用“白手起家”的模式進(jìn)入市場(chǎng)。

55 、I tanned 'em, and I pulled myself up by my bootstraps.─── 把皮染色 一舉擺脫困境

56 、For Windows Installer deployment, bootstrapping of the.NET Framework is enabled by default.───對(duì)于Windows Installer部署,.NET Framework的引導(dǎo)是默認(rèn)啟用的。

57 、Breiman’s bagging short for bootstrap aggregating is one of the earliest ensemble based algorithms.It is also one of the most intuitive and simplest to implement with a surprisingly good performance .───先翻譯一段Bagging的介紹，Breiman的bagging算法，是bootstrap aggregating的縮寫(xiě)，是最早的Ensemble算法之一，它也是最直接容易實(shí)現(xiàn)，又有著另人驚訝的好效果的算法之一。

58 、The inner bootstrapping utilizes Synonymy Thesaurus to expand pattern semantics.───內(nèi)自舉借助通用的《同義詞詞林》擴(kuò)張模式的語(yǔ)義范圍;

59 、II believe in people pulling themselves up by their bootstraps.─── 我信奉的是人應(yīng)該 扎緊腰帶 奮發(fā)圖強(qiáng) 努力往上爬

60 、Conservatives would defy our efforts at bootstrap improvements.───保守派會(huì)蔑視我們從根本上變革的努力。

61 、This value is empty if the credential is the bootstrap credential.───如果憑據(jù)是bootstrap憑據(jù),則此值為空。

62 、Dynamic Prediction for Manufacturing Errors Using Grey Bootstrap───制造誤差的灰自助動(dòng)態(tài)預(yù)報(bào)

63 、Bootstrap simulation experiment───Bootstrap模擬研究

64 、Key works: meta-analysis, nonparametric test, resampling test, bootstrap, randomization test.───基金項(xiàng)目：廣東省團(tuán)隊(duì)項(xiàng)目（003031）；

65 、Copy PXE bootstrap file in tftpboot directory.───復(fù)制PXE引導(dǎo)文件到tftpboot目錄下。

66 、weighted bootstrap inference───加權(quán)Bootstrap推斷

67 、If you are installing onto a NewWorld PowerMac you must create a special bootstrap partition to hold the boot loader.───如果您正在一臺(tái)NewWorld PowerMac上面安裝,您必須創(chuàng)建一個(gè)特殊的啟動(dòng)分區(qū)來(lái)駐留啟動(dòng)引導(dǎo)器。

68 、Build -! Internal use only! DO NOT SET THIS FLAG YOURSELF!, Used for creating build images and the first half of bootstrapping.───僅供內(nèi)部使用,請(qǐng)勿改動(dòng)!用于建立引導(dǎo)過(guò)程前半部分的鏡像構(gòu)建。

69 、Maybe I should just pull myself up by my bootstraps.─── 也許我應(yīng)該讓自己更努力點(diǎn)

70 、The Myriapoda are polyphyletic. 2.The Chilopoda appears to be sister to a clade containing the Insecta and Crustacea, but with low bootstrap support.───2、唇足綱、昆蟲(chóng)和甲殼動(dòng)物聚合，其中昆蟲(chóng)與甲殼類(lèi)聚為一支，然后與唇足綱構(gòu)成姊妹群關(guān)系, 但是支持率不高。

71 、Parametric and Bootstrap Estimations of Confidence Intervals for Analyte Concentrations of Composite Samples───參數(shù)法和非參數(shù)法估計(jì)組合樣中被測(cè)組分含量的置信區(qū)間

72 、I recoded your node bootstrap scripts so they autoinstall.─── 我重編碼了你的引導(dǎo)程序 讓它自動(dòng)安裝

73 、Bootstrapping sounds great in principle, but this apparently verdant territory is one from which few startups emerge alive.───“自助”理論聽(tīng)起來(lái)真的很不錯(cuò)，但現(xiàn)實(shí)是，很少有創(chuàng)業(yè)公司通過(guò)這樣貌似很有生機(jī)的途徑成功地生存下來(lái)。

74 、The parents looks at the world through child's view, may the better bootstrap child to know the world, and can make the parents and child's sentiment deeply.───家長(zhǎng)通過(guò)兒童的視角看世界，可以更好的引導(dǎo)兒童認(rèn)識(shí)世界，而且增進(jìn)父母與孩子的感情。

75 、A reserved section of RAM which is used to pass information from the bootstrap to the kernel.───RAM的保留段，用于將信息從引導(dǎo)程序傳到內(nèi)核。

76 、But I found my calling, and I pulled myself up by my bootstraps and started a business.─── 但我找到了自己的天職 我自力更生 改變?nèi)松?建立了一份生意

77 、For this we are considering traditional short term loans, bootstrapping where possible, and micro investments from individuals.───為此，我們考慮到傳統(tǒng)的短期貸款，如果可能的話自力更生解決，或者來(lái)自個(gè)人的小投資。

78 、Precision current source design employs bootstrap integrator.───使用自舉積分電路的精密電流源設(shè)計(jì)。

79 、Bootstrap is a technique for loading the first few instructions of a computer program into active memory and then using them to bring in the rest of the program.───如果一個(gè)軟件是很復(fù)雜的，那么在軟件啟動(dòng)的時(shí)候需要把某些結(jié)構(gòu)先載入內(nèi)存，以便于訪問(wèn)其他的軟件結(jié)構(gòu)。包括繼續(xù)啟動(dòng)軟件以及完成軟件的后續(xù)操作。

80 、The ROM monitor performs the bootstrap process and provides low-level functionality and diagnostics.───ROM監(jiān)視執(zhí)行開(kāi)機(jī)程序和提供低階的機(jī)能和診斷。

81 、In this paper,a generalized bootstrap method was proposed to estimate the yield curve for any available data sets of bond price with cubic spline interpolation method.───在一般息票剝離法(bootstrapmethod)的基礎(chǔ)上進(jìn)行了擴(kuò)展:采用三次樣條**值方法,可以對(duì)任意的國(guó)債報(bào)價(jià)數(shù)據(jù)進(jìn)行即期收益率曲線估計(jì)。

82 、At bootstrapping, the system sets up the page table for 8 MB of physical memory.───在啟動(dòng)時(shí),系統(tǒng)為8 MB的物理內(nèi)存設(shè)置頁(yè)表。

83 、Pulled up by the bootstraps, not dependent on anyone else.─── 靠自己的力量起家 而不是靠別人

84 、Performance Analysis on Two-stage Compression forward Bootstrap Air Refrigerator───雙級(jí)壓縮正升壓流程空氣制冷機(jī)性能分析

85 、Analyzing the vulnerabilities of security bootstrapping procedures in existing trusted mobile platforms, an improved procedure is proposed and it is verified according to predicate logic.───分析了現(xiàn)有可信移動(dòng)平臺(tái)安全引導(dǎo)過(guò)程安全漏洞，提出了改進(jìn)的安全引導(dǎo)過(guò)程，并通過(guò)謂詞邏輯對(duì)改進(jìn)的引導(dǎo)過(guò)程進(jìn)行了正確性驗(yàn)證。

86 、The Chilopoda appears to be sister to a clade containing the Insecta and Crustacea, but with low bootstrap support.───唇足綱、昆蟲(chóng)和甲殼動(dòng)物聚合，其中昆蟲(chóng)與甲殼類(lèi)聚為一支，然后與唇足綱構(gòu)成姊妹群關(guān)系，但是支持率不高。

87 、The values at the forks indicate the percentage of trees in which this grouping occurred after bootstrapping the data(1000 replicates; shown only when>70%).───分叉上的數(shù)值表示1000次成樹(shù)中該簇出現(xiàn)的次數(shù)百分比，僅數(shù)值>0%顯示。

88 、Determination of confidence intervals for frequency analysis by using Bootstrap───基于自助法的水文頻率區(qū)間估計(jì)

89 、In the ML analysis of combined data, the lineage (brown bear/polar bear) was more closely related to American black bear than was Asiatic black bear, however, there was low bootstrap support for this relationship.───合并數(shù)據(jù)集的系統(tǒng)發(fā)育分析表明棕熊和北極熊與美洲黑熊的關(guān)系最近，而不是亞洲黑熊，但是支持率不高。

90 、Programming is made based on VC language in this system with a variety of performance such as automatic bootstrap...───其基本功能包括文件處理、工藝參數(shù)處理、意匠圖、布面模擬、繪制小樣、編輯、小樣及布面變換等。

怎么用bootstrap方法統(tǒng)計(jì)

一、Bootstrap

非參數(shù)統(tǒng)計(jì)中一種重要的估計(jì)統(tǒng)計(jì)量方差進(jìn)而進(jìn)行區(qū)間估計(jì)的統(tǒng)計(jì)方法，也稱為自助法。其核心思想和基本步驟如下：[1]

（1）采用重抽樣技術(shù)從原始樣本中抽取一定數(shù)量（自己給定）的樣本，此過(guò)程允許重復(fù)抽樣。

（2）根據(jù)抽出的樣本計(jì)算給定的統(tǒng)計(jì)量T。

（3）重復(fù)上述N次（一般大于1000），得到N個(gè)統(tǒng)計(jì)量T。

（4）計(jì)算上述N個(gè)統(tǒng)計(jì)量T的樣本方差，得到統(tǒng)計(jì)量的方差。

應(yīng)該說(shuō)Bootstrap是現(xiàn)代統(tǒng)計(jì)學(xué)較為流行的一種統(tǒng)計(jì)方法，在小樣本時(shí)效果很好。通過(guò)方差的估計(jì)可以構(gòu)造置信區(qū)間等，其運(yùn)用范圍得到進(jìn)一步延伸。

具體抽樣方法舉例：想要知道池塘里面魚(yú)的數(shù)量，可以先抽取N條魚(yú)，做上記號(hào)，放回池塘。

進(jìn)行重復(fù)抽樣，抽取M次，每次抽取N條，考察每次抽到的魚(yú)當(dāng)中有記號(hào)的比例，綜合M次的比例，在進(jìn)行統(tǒng)計(jì)量的計(jì)算。

二、在統(tǒng)計(jì)學(xué)中，自助法（Bootstrap Method，Bootstrapping或自助抽樣法）是一種從給定訓(xùn)練集中有放回的均勻抽樣，也就是說(shuō)，每當(dāng)選中一個(gè)樣本，它等可能地被再次選中并被再次添加到訓(xùn)練集中。自助法由Bradley Efron于1979年在《Annals of Statistics》上發(fā)表。當(dāng)樣本來(lái)自總體，能以正態(tài)分布來(lái)描述，其抽樣分布(Sampling Distribution)為正態(tài)分布(The Normal Distribution)；但當(dāng)樣本來(lái)自的總體無(wú)法以正態(tài)分布來(lái)描述，則以漸進(jìn)分析法、自助法等來(lái)分析。采用隨機(jī)可置換抽樣(random samplingwith replacement)。對(duì)于小數(shù)據(jù)集，自助法效果很好。

機(jī)器學(xué)習(xí)中out of bag error怎么理解

訓(xùn)練數(shù)據(jù)集為 T ，具有M個(gè)特征

T = {(X1,y1), (X2,y2), ... (Xn, yn)}

Xi {xi1, xi2, ... xiM}，是輸入向量 yi 是標(biāo)簽.

隨機(jī)森林總結(jié):

隨機(jī)森林算法是一個(gè)分類(lèi)器算法，主要基于兩種方法

Bagging

Random subspace method.

假設(shè)在森林中我們?cè)O(shè)定s棵樹(shù)，首先我們生成 S 個(gè)和原始數(shù)據(jù)集大小一致的數(shù)據(jù)集，采用放回的隨機(jī)抽樣方法 (也即，每生成一個(gè)數(shù)據(jù)集抽樣n次).最終產(chǎn)生 數(shù)據(jù)集T1,

T2, ... TS}. 每個(gè)數(shù)據(jù)集稱作一個(gè) bootstrap 數(shù)據(jù)集. 由于放回抽樣，每個(gè)數(shù)據(jù)集 Ti 中有重復(fù)數(shù)據(jù)，Ti 相比原始數(shù)據(jù)集，可能會(huì)缺少若干記錄.這稱為Bootstrapping. (en.wikipedia.org/wiki/Bootstrapping_(statistics))

Bagging 是進(jìn)行 bootstraps & 然后將每個(gè)從 bootstrap中學(xué)到的模型進(jìn)行集成的過(guò)程

現(xiàn)在, RF 生成 S 棵樹(shù)，m

(=sqrt(M) or =floor(lnM+1)) 隨機(jī)從M個(gè)特征中抽取子特征，來(lái)創(chuàng)建樹(shù). 這叫做隨機(jī)子空間方法（random subspace method）.

所以對(duì)每個(gè)Ti bootstrap 數(shù)據(jù)集，我們創(chuàng)建了一棵樹(shù) Ki. 如果你相對(duì)某些輸入數(shù)據(jù)進(jìn)行分類(lèi) D

= {x1, x2, ..., xM} ，你讓這些數(shù)據(jù)在每棵樹(shù)上都跑一遍，從而生成 S 個(gè)預(yù)測(cè)結(jié)果 (一棵樹(shù)有一個(gè)預(yù)測(cè)結(jié)果) ，表示為 Y

= {y1, y2, ..., ys}. 最終預(yù)測(cè)結(jié)果通過(guò)大多數(shù)投票策略決定.

Out-of-bag error:

在生成s個(gè)分類(lèi)器后 (S棵樹(shù)), 對(duì)于原始訓(xùn)練集T中每個(gè)記錄 (Xi,yi) ,選擇所有不包括(Xi,yi) 的bootstrap數(shù)據(jù)集Tk.注意，這個(gè)子集，是一個(gè)boostrap 數(shù)據(jù)集所組成的集合，它們都不包含原始數(shù)據(jù)集中的某個(gè)特定記錄. 這個(gè)集合被稱作 out-of-bag 樣例. 共有n 個(gè)這樣的子集 (原始數(shù)據(jù)集 T中每行記錄對(duì)應(yīng)一個(gè)). OOB 分類(lèi)器 使用的是Tk 上投票的累積，所以它們不包含 (xi,yi).

從另外一個(gè)角度來(lái)解釋oob方法如下：

每一棵樹(shù)都通過(guò)使用不同的 bootstrap 樣本.相比原始數(shù)據(jù)集，每個(gè) bootstrap數(shù)據(jù)集中大概有1/3的記錄沒(méi)有包括進(jìn)來(lái)，也就沒(méi)有在構(gòu)建第k棵樹(shù)時(shí)候使用.

對(duì)于構(gòu)建第k棵樹(shù)時(shí)候沒(méi)有用到的每條記錄，讓它們過(guò)一遍第k棵樹(shù)，進(jìn)而獲得一個(gè)分類(lèi).通過(guò)這種方法, 對(duì)任何一條記錄來(lái)說(shuō)，大概有1/3 的樹(shù)沒(méi)有用這條記錄來(lái)構(gòu)建，因而對(duì)這些樹(shù)可以進(jìn)行測(cè)試集上的數(shù)據(jù)分類(lèi)。最終, 假設(shè) 類(lèi)別j 是當(dāng)記錄n是oob時(shí)候，獲得投票最多的類(lèi)別，j被錯(cuò)誤分類(lèi)除以總記錄數(shù)n，就是 oob error estimate. 這在很多測(cè)試中被證明是無(wú)偏的[2].

Out-of-bag 估計(jì)的泛化錯(cuò)誤率是 out-of-bag classifier 在訓(xùn)練集上的錯(cuò)誤率。

那么它為什么重要? Breiman [1996b]在對(duì) bagged 分類(lèi)器的錯(cuò)誤率估計(jì)研究中, 給出實(shí)證證據(jù)顯示，out-of-bag 估計(jì) 和使用與訓(xùn)練集大小一致的測(cè)試集所得到的錯(cuò)誤率一樣精確. 所以, 使用out-of-bag error 估計(jì)可以不在另外建立一個(gè)測(cè)試集.

參考**：http://blog.sina.com.cn/s/blog_4c9dc2a10102vl24.html