MATLAB專區(qū)：MATLAB字符串

1、MATLAB專區(qū)：MATLAB字符串                                 MATLAB真正強(qiáng)有力的地方在于它的數(shù)值處理能力。然而，經(jīng)常希望操作文本，例如把標(biāo)號(hào)和標(biāo)題放在圖上。在MATLAB里，文本當(dāng)作特征字符串或簡(jiǎn)單地當(dāng)作字符串。  

2、;      6.1  字符串            在MATLAB中的字符串一般是ASCII值的數(shù)值數(shù)組，它作為字符串表達(dá)式進(jìn)行顯示。例如，                  » t=' How about this charac

3、ter string? '              t =              How about this character string?              » size

4、(t)              ans =                   1    32              » w

5、hos                       Name        Size       Elements     Bytes    Density   Complex&#

6、160;                       ans       1 by 2             2        16

7、60;      Full      No                           t       1 by 32      &

8、#160;    32       256       Full      No             一個(gè)字符串是由單引號(hào)括起來(lái)的簡(jiǎn)單文本。在字符串里的每個(gè)字符是數(shù)組里的一個(gè)元素，字符串的存儲(chǔ)要求每個(gè)字符8個(gè)字節(jié)，如同MATLAB的其它變量。因?yàn)锳SCII字符只要求一個(gè)字節(jié)，故這種存儲(chǔ)

9、要求是浪費(fèi)的，7/8所分配的存儲(chǔ)空間無(wú)用。然而，對(duì)字符串保持同樣的數(shù)據(jù)結(jié)構(gòu)簡(jiǎn)化MATLAB的內(nèi)部數(shù)據(jù)結(jié)構(gòu)。所給出的字符串操作并不是MATLAB的基本特點(diǎn)，但這種表達(dá)是方便和可接受的。        為了了解下面字符串的ASCII表達(dá)，只需對(duì)字符串執(zhí)行一些算術(shù)運(yùn)算。最簡(jiǎn)單和計(jì)算上最有效的方法是取數(shù)組的絕對(duì)值。例如，        » u=abs(t)    u =   

10、   Columns 1 through 12         72   111   119    32    97    98   111   117   116    32   116   104    &

11、#160; Columns 13 through 24        105   115    32    99   104    97   114    97    99   116   101   114     

12、Columns 25 through 32         32   115   116   114   105   110   103    63        » u=t+0    u =     

13、; Columns 1 through 12         72   111   119    32    97    98   111   111 2 3 4 5 下一頁(yè)           &#

14、160;                                    7   116    32   116   104   &#

15、160;  Columns 13 through 24        105   115    32    99   104    97   114    97    99   116   101   114    &#

16、160; Columns 25 through 32         32   115   116   114   105   110   103    63            在上面后一個(gè)例子里，加零到字符串也改變了它的ASCII的表示。函數(shù)<B 

17、   style="mso-bidi-font-weight: normal">setstr提供了逆轉(zhuǎn)換。                           » v=setstr(u)       &#

18、160;               v =                       How about this character string?       &

19、#160;因?yàn)樽址菙?shù)值數(shù)組，它們可以用MATLAB中所有可利用的數(shù)組操作工具進(jìn)行操作。例如，                                     » u=t(16:24)   

20、                              u =                    &#

21、160;            character        字符串象數(shù)組一樣進(jìn)行編址。這里元素16到24包含單詞<I    style="mso-bidi-font-style: normal">character          

22、;                           » u=t(24:-1:16)                    &#

23、160;            u =                                 retcarahc    

24、    這是單詞<I    style="mso-bidi-font-style: normal">character的反向拼寫。                              

25、;                » u=t(16:24)'                                

26、;           u =                                       &

27、#160;  c    上一頁(yè)  1 2 3 4 5 下一頁(yè)                                    

28、;                                                  

29、0;   h                                          a      

30、                                    r              

31、0;                           a                        &

32、#160;                 c                                 

33、;         t                                          e&

34、#160;                                         r        用轉(zhuǎn)置算子

35、將單詞<I    style="mso-bidi-font-style: normal">character變換成一個(gè)列。                           » v=' I can''t find the manua

36、l! '                       v =                       I can't find the ma

37、nual!        字符串內(nèi)的單引號(hào)是由兩個(gè)連續(xù)的單引號(hào)來(lái)表示。    字符串連接可以直接從數(shù)組連接中得到。                  » u=' If a woodchuck could chuck wood, ' ;    &

38、#160;         » v=' how much wood would a woodchuck chuck? ' ;              » w=u  v              w = 

39、             If a woodchuck could chuck wood, how much wood would a woodchuck chuck?            函數(shù)<B    style="mso-bidi-font-weight: normal">disp允許不打

40、印它的變量名而顯示一個(gè)字符串。例如，                           »disp(u)     &nb上一頁(yè)  1 2 3 4 5 下一頁(yè)   

41、0;                                                sp;   

42、;              If a woodchuck could chuck wood,        注意<B    style="mso-bidi-font-weight: normal">u = 語(yǔ)句被去掉了。這對(duì)腳本文件內(nèi)顯示幫助的文本有用。     &

43、#160;  如同矩陣，字符串可以有多個(gè)行，但每行必須有相同數(shù)目的列數(shù)。因此，顯然要用空格以使所有行有相同長(zhǎng)度，例如，                           » v=' Character strings having more  than '   

44、                        ' one row must have the same number '                    &

45、#160;      ' of column just like matrices!        '                       v =        &#

46、160;              Character strings having more than                       one row must have the same number   

47、0;                    of column just like matrices!            考慮下面例子，它把一個(gè)字符串轉(zhuǎn)換成大寫。首先，函數(shù)<B    style="mso-bidi-font-weight:

48、 normal">find用來(lái)找出小寫字符的下標(biāo)值，然后，從小寫元素中只減去小寫與大寫之差，最后，用<B    style="mso-bidi-font-weight: normal">setstr把求得的數(shù)組轉(zhuǎn)換成它的字符串表示。                  » disp(u)    

49、;          If a woodchuck could chuck wood,                  » i=find(u>=' a ' & u<= ' z ');     %  find is a very

50、 powerful function!                  » u(i)=setstr(u(i)-(' a '-' A ')              u =       &

51、#160;      IF A WOODCHUCK COULD CHUCK WOOD,            事實(shí)上，如在3.7節(jié)所描述的，矩陣能由單個(gè)下標(biāo)標(biāo)識(shí)。而不是由行和列下標(biāo)標(biāo)識(shí)，所以上面例子對(duì)字符串矩陣<B    style="mso-bidi-font-weight: normal">v也同樣適用：     

52、;             » disp(v)              Character strings having more than              one row must have th

53、e same number               of column just like matrices!         » i=find(v>=' a ' & v<=' z ');     %  here i is a single index vector int

54、o v,                  » v(i)=setstr(v(i)-(' a '-' A ')     %上一頁(yè)  1 2 3 4 5 下一頁(yè)          &

55、#160;                                           and matrix keeps the same orientation.  &#

56、160;           v =              CHARACTER STRINGS HAVING MORE THAN              ONE ROW MUST HAVE THE SAME NUMBER  

57、             OF COLUMN JUST LIKE MATRICES!            最后，當(dāng)使用前面腳本文件這一章節(jié)中的函數(shù)<B    style="mso-bidi-font-weight: normal">input時(shí)，字符串是很有用的。  

58、0;                        » t=' Enter number of rolls of tape > ' ;                 

59、      » tape=input(t)                       Enter number of rolls of tape > 5