計(jì)算機(jī)專業(yè)畢業(yè)設(shè)計(jì)-外文翻譯--matlab 介紹

1、<p><b>　　外文原文</b></p><p>　　Introduction to MATLAB</p><p>　　MATLAB (short for Matrix Laboratory) is a special-purpose computer program optimized to perform engineering and scient

2、ific calculations. It started life has a program designed to perform matrix mathematics, but over the years it has grown into a flexible computing system capable of solving essentially any technical problem.</p>&

3、lt;p>　　The MATLAB program implements the MATLAB programming language and provides an extensive library of predefined functions that make technical programming tasks easier and more efficient. This book introduces the

4、MATLAB language and shows how to use it to solve typical technical problems.</p><p>　　MATLAB is a huge program, with an incredibly rich variety of functions. Even the basic version of MATLAB without any tool

5、kits is much richer than other technical programming languages. There are more than 1000 functions in the basic MATLAB product alone，and the toolkits extend this capability with many more functions in various specialtie

6、s. This book makes no attempt to introduce the user to all of MALTLAB′s own tools to locate the correct function for a specific purpose from the enormous choi</p><p>　　Advantages of MATLAB</p><p&

7、gt;　　MATLAB has many advantages compared with conventional computer languages for technical problem solving. Among them are the following:</p><p>　　Ease of Use</p><p>　　MATLAB is an interpreted

8、language, like many versions of Basic. Like Basic, it is very easy to use. The program can be used as a scratch pad to evaluate expressions typed at the command line, or it can be used to execute large prewritten program

9、s. Programs may be easily written and modified with the built-in integrated development environment, and debugged with the MATLAB debugger. Because the language is so easy to use, it is ideal for educational use, and for

10、 the rapid prototyping of new progr</p><p>　　Many program development tools are provided to make the program easy to use. a workspace browser, and extensive demos.</p><p>　　Platform independence

11、 </p><p>　　MATLAB is supported on many different computer systems, providing a large measure of platform independence. At the time of this writing, the language is supported on windows 9x/NT/2000 and many di

12、fferent versions of UNIX. Programs written on any platform will run on all of the other platforms, and data files written on any platform may be read transparently on any other platforms, AS a result,</p><p>

13、;　　Programs written in MATLAB can migrate to new platforms when the needs of the user change.</p><p>　　Predefined Functions</p><p>　　MATLAB comes complete with an extensive library of predefined

14、 functions that provide tested and prepackaged solutions to many basic technical tasks. For example, suppose that you are writing a program that must calculate the statistics associated with an input data set. In most la

15、nguages, you would need to write your own subroutines or functions to implement calculations such as the arithmetic mean, standard deviation, median, and so forth. These and hundreds of other functions are built right i&

16、lt;/p><p>　　In addition to the large library of functions built into the basic MATLAB language, many special-purpose toolboxes are available to help solve complex problems in specific areas. For example, a user

17、 can buy standard toolboxes to solve problems in Signal Processing, Control Systems, Communications, Image Processing, and Neural Networks, among many others. There is also an extensive collection of free user-contribute

18、d MATLAB programs that are shared through the MATLAB Web site.</p><p>　　Device-Independent Plotting</p><p>　　Unlike most other computer languages, MATLAB has many integral plotting and imaging c

19、ommands. The plots and images can be displayed on any graphical output device supported by the computer on which MATLAB is running. This capability makes MATLAB an outstanding tool for visualizing technical data.</p&g

20、t;<p>　　Graphical User Interface</p><p>　　MATLAB includes tools that allow a programmer to interactively construct a graphical user interface (GUI) for his or her program. With this capability, the pr

21、ogrammer can design sophisticated data analysis programs that can be operated by relatively inexperienced users.</p><p>　　MATLAB Compiler</p><p>　　MATLAB′s flexibility and platform independence

22、is achieved by compiling MATLAB programs into a device-independence p-code, and then interpreting the p-code instructions at run time. This approach is similar to that used by Microsoft is Visual Basic language. Unfortun

23、ately, the resulting programs can sometimes execute slowly because the MATLAB code is interpreted rather than compiled. We will point out features that tend to slow program execution when we encounter them.</p>&l

24、t;p>　　A separate MATLAB compiler is available. This compiler can compile a MATLAB program into a true executable that runs faster than the interpreted code. It is a great way to convert a prototype MATLAB program into

25、 an executable suitable for sale and distribution to users.</p><p>　　Disadvantages of MATLAB</p><p>　　MATLAB has two principal disadvantages. The first is that it is an interpreted language, and

26、 therefore can execute more slowly than compiled languages. This problem can be mitigated by properly structuring the MATLAB program and by the use of the MATLAB compiler to compile the final MATLAB program before distri

27、bution and general use.</p><p>　　The second disadvantage is cost: A full copy of MATLAB is 5 to 10 times more expensive than a conventional C or Fortran compiler. This relatively high cost is more than offs

28、et by the reduced time required for an engineer or scientist to create a working program, so MATLAB is cost-effective for businesses. However, it is too expensive for most individuals to consider purchasing. Fortunately,

29、 there is also an inexpensive Student Edition of MATLAB, which is a great tool for students wanting to lea</p><p>　　With the introduction of branches and loops, our programs are going to become more complex,

30、 and it will get easier to make mistakes. To help avoid programming errors, we will introduce a formal program design procedure based on the technique known as top-down design. We will also introduce a common algorithm d

31、evelopment tool known as pseudo code.</p><p>　　Introduction To Top-Down Design Techniques</p><p>　　Suppose that you are an engineer working in industry, and that you need to write a program to s

32、olve some problem. How do you begin?</p><p>　　When given anew problem, there is a natural tendency to sit down at a keyboard and start programming without “wasting” a lot of time thinking about the problem f

33、irst. It is often possible to get away with this “on the fly” approach to programming for very small problems, such as many of the examples in this book. In the real world, however, problems are larger, and a programmer

34、attempting this approach will become hopelessly bogged down. For larger problems, it pays to completely think out the p</p><p>　　We introduce a formal program design process in this section, and then apply t

35、hat process to every major application developed in the remainder of the book. For some of the simple examples that we will be doing, the design process will seem like overkill; however, as the problems that we solve get

36、 larger and larger, the process becomes more and more essential to successful programming.</p><p>　　When I was an undergraduate, one of my professors was fond of saying, “programming is easy. It is knowing w

37、hat to program that is hard.” his point was forcefully driven home to me after I left university and began working in industry on larger scale software projects. I found that the most difficult port of my job was to unde

38、rstand the problem I was trying to solve. Once I really understood the problem, it became easy to break the problem apart into smaller, more easily manageable pieces with we</p><p>　　Top-down design is the p

39、rocess of starting with a large task and breaking it down into smaller, more easily understandable pieces, which perform a portion of the desired task. Each subtask may in turn be subdivided into smaller subtasks if nece

40、ssary. Once the program is divided into small pieces, each piece can be coded and tested independently. We do not attempt to combine the subtasks into a complete task until each of the subtasks has been verified to work

41、properly by itself.</p><p>　　The concept of top-down design is the basis of our formal program design process. We will now introduce the details of the process, which is illustrated in figure 1 the steps inv

42、olved are:</p><p>　　Clearly state the problem that you are trying to solve.</p><p>　　Programs are usually written to fill some perceived need, but that need may not be articulated clearly by the

43、 person requesting the program. For example, a user may ask for a program to solve a system of simultaneous linear equations. This request is not clear enough to allow a programmer to design a program to meet the need; h

44、e or she must first know much more about the problem to be solved. Is the system of equations to be solved real or complex? What is the maximum number of equations and unk</p><p><b>　　Figure 1</b>

45、;</p><p>　　Design and write a program to solve a system of simultaneous linear equations having real coefficients and with up to 20 equations in 20 unknowns.</p><p>　　Define the inputs required

46、by the program and the outputs to be produced by the program.</p><p>　　The inputs to the program and the outputs produced by the program must be specified so that the new program will properly fit into the o

47、verall processing scheme. In this example, the coefficients of the equations to be solved are probably in some pre-existing order, and our new program needs to be able to read them in that order. And our new program need

48、s to be able to read them in that order. Similarly, it needs to produce the answers required by the programs that may follow it in the overall p</p><p>　　Design the algorithm that you intend to implement in

49、the program.</p><p>　　An algorithm is a step-by-step procedure for finding the solution to a problem. It is at this stage in the process that top-down design techniques come into play. The designer looks for

50、 logical divisions within the problem, and divides it up into subtasks along those lines. This process is called decomposition. If the subtasks are large, the designer can break them up into even smaller sub-tasks. This

51、process continues until the problem has been divided into many small pieces, each of which does</p><p>　　After the problem has been decomposed into small pieces, each piece is further refined through a proce

52、ss called stepwise refinement. In stepwise refinement, a designer starts with a general description of what the piece of code should do, and then defines the functions of the piece in greater and greater detail until the

53、y are specific enough to be turned into MATLAB statements. Stepwise refinement is usually done with pseudo code, which will be described in the next section.</p><p>　　It is often helpful to solve a simple

54、 example of the problem by hand during the algorithm development process. If the designer understands the steps that he or she went through in solving the problem by hand, then he or she will be better able to apply deco

55、mposition and stepwise refinement to the problem.</p><p>　　Turn the algorithm into MATLAB statements.</p><p>　　If the decomposition and refinement process was carried out properly, this step wil

56、l be very simple. All the programmer will have to do is to replace pseudo code with the corresponding MATLAB statements on a one-for-one basis.</p><p>　　Test the resulting MATLAB program</p><p>

57、　　This step is the real killer. The components of the program must first be tested individually, if possible, and then the program as a whole must be tested. When testing a program, we must verify that it works correctly

58、 for all legal input data sets. It is very common for a program to be written, tested with some standard data set, and released for use, only to find that it produces the wrong answers (or crashes) with a different input

59、 data set. If the algorithm implemented in a program includes </p><p>　　Large programs typically go through a series of tests before they are released for general use (see Figure 2). The first stage of testi

60、ng is sometimes called unit testing. During unit testing, the individual subtasks of the program are tested separately to confirm that they work correctly. After the unit testing is completed, the program goes through a

61、series of builds, during which the individual subtasks are combined to produce the final program. The first build of the program typically includ</p><p><b>　　Figure 2</b></p><p><

62、b>　　中文翻譯</b></p><p><b>　　MATLAB 介紹</b></p><p>　　MATLAB (矩陣實(shí)驗(yàn)室的簡稱)是一種專業(yè)的計(jì)算機(jī)程序，用于工程科學(xué)的矩陣數(shù)學(xué)運(yùn)算。但在以后的幾年內(nèi)，它逐漸發(fā)展為一種極其靈活的計(jì)算體系，用于解決各種重要的技術(shù)問題。</p><p>　　MATLAB 程序執(zhí)行MATLAB

63、語言，并提供了一個(gè)極其廣泛的預(yù)定義函數(shù)庫，這樣就使得技術(shù)工作變得簡單高效。本書將介紹MATLAB 語言，并向大家展示如何運(yùn)用它去解決經(jīng)典的技術(shù)問題。</p><p>　　MATLAB 是一個(gè)龐大的程序，擁有難以置信的各種豐富的函數(shù)；即使基本版本的MATLAB 語言擁有的函數(shù)也比其他的工程編程語言要豐富的多?；镜腗ATLAB 語言已經(jīng)擁有了超過1000 多個(gè)函數(shù)，而它的工具包帶有更多的函數(shù)，由此擴(kuò)展了它在許多專業(yè)

64、領(lǐng)域的能力。本書無意將MATLAB 的所有函數(shù)介紹給大家，而是讓大家掌握編寫調(diào)試和優(yōu)化程序的基本功，還有一些重要函數(shù)的子集。所以從大量可利用的函數(shù)中篩選出你所需要的函數(shù)就顯得尤為重要。</p><p>　　MATLAB 的優(yōu)點(diǎn)</p><p>　　MATLAB 語言相對(duì)于傳統(tǒng)的科技編程語言有諸多的優(yōu)點(diǎn)。主要包括：</p><p><b>　　1.易用性&l

65、t;/b></p><p>　　MATLAB 是種解釋型語言，就像各種版本的BASIC。和BASIC 一樣，它簡單易用程序可用作便箋簿求打在命令行處表達(dá)式的值，也可執(zhí)行預(yù)先寫好的大型程序。在MATLAB 集成開發(fā)環(huán)境下，程序可以方便的編寫，修改和調(diào)試。這是因?yàn)檫@種語言極易使用，對(duì)于教育應(yīng)用和快速建立新程序的原型，它是一個(gè)理想的工具。許多的編程工具使得 MATLAB 十分簡單易用。這些工具包括：一個(gè)集成的編譯

66、/調(diào)試器，在線文件手冊(cè)，工作臺(tái)和擴(kuò)展范例。</p><p><b>　　2.平臺(tái)獨(dú)立性</b></p><p>　　MATLAB 支持許多的操作系統(tǒng)，提供了大量的平臺(tái)獨(dú)立的措施。在本書編寫的時(shí)侯， windows98/2000/NT 和許多版本的UNIX 系統(tǒng)都支持它。在一個(gè)平臺(tái)上編寫的程序，在其它平臺(tái)上一樣可以正常運(yùn)行，在一個(gè)平臺(tái)上編寫的數(shù)據(jù)文件在其它平臺(tái)上一樣可以

67、編譯。因此用戶可以根據(jù)需要把MATLAB 編寫的程序移植到新平臺(tái)。</p><p><b>　　3.預(yù)定義函數(shù)</b></p><p>　　MATLAB 帶有一個(gè)極大的預(yù)定義函數(shù)庫，它提供了許多已測(cè)試和打包過的基本工程問題的函數(shù)。例如，假設(shè)你正在編寫一個(gè)程序，這個(gè)程序要求你必須計(jì)算與輸入有關(guān)的統(tǒng)計(jì)量。在許多的語言中，你需要寫出你所編數(shù)組的下標(biāo)和執(zhí)行計(jì)算所需要的函數(shù)，這

68、些函數(shù)包括其數(shù)學(xué)意義，中值，標(biāo)準(zhǔn)誤差等。像這樣成百上千的函數(shù)已經(jīng)在MATLAB 中編寫好，所以讓編程變得更加簡單。</p><p>　　除了植入MATLAB 基本語言中的大量函數(shù)，還有許多專用工具箱，以幫助用戶解決在具體領(lǐng)域的復(fù)雜問題。例如，用戶可以購買標(biāo)準(zhǔn)的工具箱以解決在信號(hào)處理，控制系統(tǒng)，通信，圖象處理，神經(jīng)網(wǎng)絡(luò)和其他許多領(lǐng)域的問題。</p><p><b>　　4.機(jī)制獨(dú)立

69、的畫圖</b></p><p>　　與其他語言不同，MATLAB 有許多的畫圖和圖象處理命令。當(dāng)MATLAB 運(yùn)行時(shí)，這些標(biāo)繪圖和圖片將會(huì)出現(xiàn)在這臺(tái)電腦的圖像輸出設(shè)備中。此功能使得MATLAB 成為一個(gè)形象化技術(shù)數(shù)據(jù)的卓越工具。</p><p><b>　　5.用戶圖形界面</b></p><p>　　MATLAB 允許程序員為他們

70、的程序建立一個(gè)交互式的用戶圖形界面。利用MATLAB 的這種功能，程序員可以設(shè)計(jì)出相對(duì)于無經(jīng)驗(yàn)的用戶可以操作的復(fù)雜的數(shù)據(jù)分析程序。</p><p>　　6.MATLAB 編譯器</p><p>　　MATLAB 的靈活性和平臺(tái)獨(dú)立性是通過將MATLAB 代碼編譯成設(shè)備獨(dú)立的P 代碼，然后在運(yùn)行時(shí)解釋P 代碼來實(shí)現(xiàn)的。這種方法與微軟的VB 相類似。不幸的是，由于MATLAB 是解釋性語言，而

71、不是編譯型語言，產(chǎn)生的程序執(zhí)行速度慢。當(dāng)我們遇到執(zhí)行速度慢的程序時(shí)，我們將會(huì)指出其這一特性。</p><p>　　MATLAB 的缺點(diǎn)</p><p>　　MATLAB 有兩個(gè)基本的缺點(diǎn)。</p><p>　　第一，它是解釋型語言，其執(zhí)行速度要比編譯型語言慢得多。這個(gè)問題可以通過合理的MATLAB 結(jié)構(gòu)得到緩解，也可以在發(fā)行廣泛使用前編譯出MATLAB 程序。<

72、;/p><p>　　第二，他的費(fèi)用較高。一個(gè)完全版MATLAB 編譯器的大小是一個(gè)C 語言或Fortan 語言編譯器的5 到10倍。但MATLAB 能夠節(jié)省大量的時(shí)間在科技編程方面，故MATLAB 在商業(yè)編程過程中是節(jié)省成本的。盡管如此，相對(duì)于大多數(shù)考慮購買的人還是很昂貴的。幸運(yùn)的是，它有一個(gè)價(jià)格便宜的學(xué)生專用版本，對(duì)學(xué)生來說它是學(xué)習(xí)MATLAB 語言的一個(gè)重要工具。學(xué)生版的MATLAB和完全版的MATLAB 是基本

73、一致的。隨著選擇和循環(huán)介紹，我們的程序也將變得復(fù)雜，對(duì)于解決問題來說，將會(huì)變得簡單。為了幫助大家避免在編程過程中出現(xiàn)大量的錯(cuò)誤，我們將向大家介紹正式的編程步驟，即自上而下的編程方法。我們也會(huì)向大家介紹一些普通的算法開發(fā)工具即偽代碼。</p><p>　　自上而下的編程方法簡介</p><p>　　假設(shè)你是在工廠工作的工程師，為了解決某些問題，你要編寫一個(gè)程序。你如何開始呢？當(dāng)遇到一個(gè)新問題

74、時(shí)，我們的心里會(huì)自然而然的產(chǎn)生這樣的想法：馬上坐在計(jì)算機(jī)前，開始編程，而不用浪費(fèi)大量的時(shí)間思考我們所要解決的問題是什么？用這種不切實(shí)際的想法來編一些非常小的程序可能會(huì)成功。但在現(xiàn)實(shí)中，問題可能會(huì)非常的大，程序員再用這種方法編程將會(huì)陷入困境。對(duì)于一個(gè)大的程序來說，在編寫代碼之前你要通盤的思考你所要面臨的問題和解決的方法。在本節(jié)中，我們將向大家介紹正式的編程設(shè)計(jì)步驟，然后應(yīng)用這個(gè)步驟來編寫本書所有的大的應(yīng)用程序。對(duì)于我們所遇到一些簡單的例子

75、來說，這個(gè)步驟好像有些畫蛇添足。但是當(dāng)我們解決的問題變得越來越大的時(shí)侯，這個(gè)步驟將會(huì)變得異常重要。當(dāng)我還沒有畢業(yè)的時(shí)侯，一個(gè)教授喜歡說：“編程很簡單，因?yàn)槲抑涝诰幊痰倪^程的困難”。當(dāng)我們離開學(xué)校，在工廠從事于大規(guī)模軟件工程編寫時(shí)，我深深地理解了它所說的話。我發(fā)現(xiàn)在工作中我遇到的大多數(shù)困難都是對(duì)所要解決問題的理解。一旦你真正理解了問題，你就會(huì)把這個(gè)問題分解成許多小的問題，更加易于管理的小塊，然后逐一解決某一個(gè)小塊。自上而下的編程方法是我

76、們正規(guī)編程設(shè)計(jì)的基礎(chǔ)。我們</p><p>　　說明的步驟細(xì)節(jié)。步驟如下:</p><p>　　1.清晰地陳述你所要解決的問題</p><p>　　編寫的程序大多數(shù)情況下要滿足一些感覺上的需要，但這種需要不一定能夠被人清晰地表達(dá)出來。例如，用戶需要一個(gè)解線性方程組的表達(dá)式。像這樣的要求就不夠清楚，程序員就很難編出一個(gè)使他滿意的程序。他必須弄清楚要有多少問題需要解決?

77、在這些方程式中有沒有對(duì)稱的形式使我們的開發(fā)變得簡單?程序設(shè)計(jì)者必須和使用者討論所需的程序，他們必須要對(duì)完成的任務(wù)有一個(gè)精確細(xì)致的描述。對(duì)問題清晰的描述可以防止誤解，并且能夠幫助程序員合理的組織他的思想。上面的例子對(duì)問題合適的陳述應(yīng)為:設(shè)計(jì)一個(gè)用于解決聯(lián)立線性方程組的程序，這些方程中未知數(shù)的系數(shù)為實(shí)數(shù)，最多有20 個(gè)未知數(shù)。</p><p>　　2.定義程序所需的輸入量和程序所產(chǎn)生的輸出量</p>&

78、lt;p>　　指定輸入量和輸出量，只有這樣新的程序才能適應(yīng)全過程計(jì)劃。在這個(gè)例子中方程式的系數(shù)可能有其預(yù)先存在的順序，我們的新程序必須能按照順序讀取它們。相似地，也需要產(chǎn)生出這個(gè)程序所要求的結(jié)果，即輸出量，我們還要以一定的格式打印出來。</p><p>　　3.設(shè)計(jì)你的程序得以實(shí)現(xiàn)的算法</p><p><b>　　圖 1</b></p><

79、p>　　算法是指為某個(gè)問題找到答案一步接一步的程序。在這個(gè)階段自上而下的編程方法發(fā)揮了作用。編程設(shè)計(jì)者開始對(duì)這個(gè)問題進(jìn)行邏輯劃分，把它逐步分解為一個(gè)又一個(gè)子工作。這個(gè)過程叫做分解(decomposition)。如果一些子工作還是比較大，設(shè)計(jì)者還可以把他它分解成更小的塊。這個(gè)過程將會(huì)繼續(xù)到問題被分解成許多簡單且易理解的小塊為止。在問題被分解成小塊之后，每一個(gè)小塊要被進(jìn)一步的求精，這個(gè)過程叫做逐步求精(stepwise refinem

80、ent)。在這個(gè)過程中，設(shè)計(jì)者開始于對(duì)本小塊代碼總括性的描述，然后開始一步一步地定義所需的函數(shù)，越來越具體，直到他能夠轉(zhuǎn)化為MATLAB 語句。逐步求精的過程中，我們要用到的偽代碼將會(huì)在下節(jié)為大家介紹。在算法開發(fā)過程中，這個(gè)方法是非常有用的。如果設(shè)計(jì)者真正理解了解決問題這個(gè)些步驟，他將會(huì)對(duì)問題進(jìn)行分解和逐步求精。</p><p>　　4.把算法轉(zhuǎn)化為代碼</p><p>　　如果分解和逐步

81、求精的過程已經(jīng)順利完成，那么這一步將會(huì)異常地簡單。所有程序員都會(huì)將偽代碼一句一句地轉(zhuǎn)化為合適地MATLAB 語句。</p><p>　　5.檢測(cè)產(chǎn)生的MATLAB 程序</p><p>　　這一步是真正的攔路虎。首先，程序的每一部分將會(huì)被單獨(dú)地檢測(cè)，如果有可能的話，整個(gè)程序還要被檢測(cè)一遍。在我們檢測(cè)程序時(shí)，我們必須證明所有合法輸入數(shù)據(jù)值都能夠正常運(yùn)行。用標(biāo)準(zhǔn)的輸入值檢測(cè)程序，看它是否產(chǎn)生了

82、值。如果在一個(gè)程序中執(zhí)行的算法包含了不同的分支，你必須檢測(cè)每一個(gè)分支，以保證產(chǎn)生正確的答案。大程序在交付大眾使用之前，必須經(jīng)過一系列地檢測(cè)(圖2)。檢測(cè)的第一步有時(shí)被稱為單元檢測(cè)(unittesting)。在單元檢測(cè)過程中，程序的子程序?qū)?huì)被獨(dú)立地檢測(cè)以證明它的正確性。當(dāng)單元檢測(cè)結(jié)束之后，這個(gè)程序?qū)⑦M(jìn)行一系列的組合，把獨(dú)立的子程序聯(lián)合產(chǎn)生出最后的程序。</p><p>　　程序第一步的聯(lián)合通常只包括很少的子程序。