精通matlab綜合輔導(dǎo)與指南附例程chap6

6文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。MATLABASCII值的數(shù)值數(shù)組，它作為字符串表達(dá)式進(jìn)行顯示。?t='Howaboutthischaracterstring?'t=Howaboutthischaracterans= ?1by2t1by一個(gè)字節(jié)，故這種存儲(chǔ)要求是浪費(fèi)的，7/8所分配的存儲(chǔ)空間無用。然而，對(duì)字符串保持同MATLABMATLAB的基u=Columns1through Columns13through Columns25through ?u=t+0u=Columns1through Columns13through Columns25through v=Howaboutthischaracter?u=?u=t(24:-u=?r?v='Ican''tfindthemanual!'v=Ican'tfindthe?u='Ifawoodchuckcouldchuckwood,'?v='howmuchwoodwouldawoodchuckchuck?'?w=[u w=Ifawoodchuckcouldchuckwood,howmuchwoodwouldawoodchuckIfawoodchuckcouldchuck=?v=['Characterstringshavingmore 'onerowmusthavethesamenumber'ofcolumnjustlike vCharacterstringshavingmorethanonerowmusthavethesamenumberofcolumnjustlikematrices!find用來找出小寫字符的下?Ifawoodchuckcouldchuck?i=find(u>='a'&u<='z findisaverypowerful?u(i)=setstr(u(i)-('a'-'A'))u=IFAWOODCHUCKCOULDCHUCK以上面例子對(duì)字符串矩陣v也同樣適用：?Characterstringshavingmorethanonerowmusthavethesamenumberofcolumnjustlikematrices!?i=find(v>='a'&v<='z hereiisasingleindexvectorinto?v(i)=setstr(v(i)-('a'-'A')) andmatrixkeepsthesameorientation.v=CHARACTERSTRINGSHAVINGMORETHANONEROWMUSTHAVETHESAMENUMBEROFCOLUMNJUSTLIKEMATRICES!?t='Enternumberofrollsoftape>'?Enternumberofrollsoftape>5tape=5?x=input('Enteranything>','sEnteranything>anythingcanbeenteredx=anythingcanbeinput里的附加參量’s’MATLAB，作為一個(gè)字符串，只要把用戶輸字 ? ?t=['Acircleofradius 'hasanareaof' '.']?Acircleofradius hasanarea num2str用來把數(shù)值轉(zhuǎn)換成字符串，字符串連接用來把所轉(zhuǎn)換的數(shù)嵌人到一個(gè)字符串句子中。按類似方式，int2strnum2strint2str都調(diào)用函數(shù)sprintf，它用類似C語言語法把數(shù)值轉(zhuǎn)換成字符串。?fprintf('Seewhatthisdoes')Seewhatthisdoes??fprintf('Seewhatthisdoes\n')Seewhatthisdoes第二個(gè)例子里，\n插入一個(gè)新行字符，在MATLAB提示符出現(xiàn)之前創(chuàng)建一個(gè)新行。fprintfsprintffprintf把輸出送到顯示屏或文件中，而sprintf把輸出返回到一個(gè)字符串中。例如，上面的例子用num2str可重寫為?t=sprintf('Acircleofradius%.4ghasanareaof%.4g.',rad,?Acircleofradius2.5hasanareaof?fprintf('Acircleofradius%.4ghasanareaof%.4g.\n',rad,area)Acircleofradius2.5hasanareaof19.63.這里%.4gnum2str中的數(shù)據(jù)格式。%.4g就是用指數(shù)或定點(diǎn)標(biāo)記，不管哪在各種不同轉(zhuǎn)換下，如何顯示pi結(jié)果。數(shù) fprintf('%.0e\n',pi)fprintf('%.1e\n',pi)fprintf('%.3e\n',pi)fprintf('%.5e\n

fprintf('%.10e\nfprintf('%.0f\n3fprintf('%.1f\nfprintf('%.3f\nfprintf('%.5f\nfprintf('%.10f\nfprintf('%.0g\n3fprintf('%.1g\n3fprintf('%.3g\nfprintf('%.5g\nfprintf('%.10g\nfprintf('%.8.0g\n3fprintf('%.8.1g\n3fprintf('%.8.3g\nfprintf('%.8.5g\nfprintf('%.8.10g\nef8位。和sprintf是有用的。?a='one';b='two';c='three'?disp(str2mat(a,b,c,'four'))?s='[1 s= 2; ?4] astringofaMATLABans?s='123e+5%astringcontainingasimples?ansstr2num不能接受用戶定義的變量，也不能執(zhí)行轉(zhuǎn)換過程的算術(shù)運(yùn)算。更多的信字 ?a=eval('sqrt(2)')a=?eval('a=sqrt(2)')a=?eval('a=sqrtt(2)','a=[ a= 數(shù)。這種形式經(jīng)常被描述為eval(try,catch)。fevaleval類似，但在用法上有更多的限制。feval('funx)求由字符串'fun'給定的函數(shù)值，其輸入?yún)⒘渴亲兞縳。即feval('fun',x)等價(jià)于求fun(x)值。例如，?a=feval('sqrt',2)a=參量的函數(shù)值，例如，feval('fun',x,y,z)等價(jià)于求fun(x,y,z)值。?b='PeterPiperpickedapeckofpickledpeppers'?findstr(b,' findspaceans= ?findstr(b,'p') findtheletterpans= ?find(b=='p') %forsinglecharactersearchesthefindcommandworkstooans= ?findstr(b,'cow') findthewordcowans= ?findstr(b,'pick') findthestringpickans= ?strrep(b,'p','P') capitalizeallp'sans=PeterPiPerPickedaPeckofPickled?strrep(b,'Peter','Pamela') changePetertoPamelaans=PamelaPiperpickedapeckofpickled函數(shù)strtok找出由特定字符指定的字符串內(nèi)的標(biāo)記，空格是缺省限定字符。例如，?PeterPiperpickedapeckofpickled?strtok(b) findfirsttokeninabovestringseparatedbywhitespaceans=?[c,r]=strtok(b) returntheremainderofthestringarrayinrc=r=Piperpickedapeckofpickled?[d,s]=strtok(r)%fi