matlab_08_talk8 第八講 Matlab編程-II

1、 MatlabMatlab計算與仿真計算與仿真 n第七講回顧第七講回顧 nMatlab編程編程-II - 函數(shù)初識函數(shù)初識 - 控制語句控制語句 - 函數(shù)變量函數(shù)變量 第八講提綱第八講提綱 MatlabMatlab計算與仿真計算與仿真 第七講回顧第七講回顧 n程序的概念與結(jié)構(gòu)程序的概念與結(jié)構(gòu) - 程序程序: 數(shù)據(jù)結(jié)構(gòu)數(shù)據(jù)結(jié)構(gòu)+算法算法 - 結(jié)構(gòu)結(jié)構(gòu): 順序順序/選擇選擇/循環(huán)循環(huán) n編程的環(huán)境和工具編程的環(huán)境和工具 - m 文件編輯器文件編輯器 nm 文件及函數(shù)文件及函數(shù) - m文件文件: 腳本文件腳本文件/函數(shù)文件函數(shù)文件 - 函數(shù)函數(shù): 主函數(shù)主函數(shù)/子函數(shù)子函數(shù)/ MatlabMatla

2、b計算與仿真計算與仿真 Matlab編程編程 (續(xù)續(xù)) - m-函數(shù)及子函數(shù)實例函數(shù)及子函數(shù)實例 1：function mean,stdev = stat(x) % 主函數(shù)定義主函數(shù)定義 2：% STAT Interesting statistics. 3：n = length(x); % 數(shù)據(jù)個數(shù)查詢數(shù)據(jù)個數(shù)查詢 4：mean = avg(x,n); % 子函數(shù)調(diào)用子函數(shù)調(diào)用 5：stdev = sqrt(sum(x-avg(x,n).2)/n); 6：%- 7：function mean = avg(x,n) % 子函數(shù)定義子函數(shù)定義 8：%AVG subfunction 9：mean =

3、 sum(x)/n; %內(nèi)嵌函數(shù)調(diào)用內(nèi)嵌函數(shù)調(diào)用 MatlabMatlab計算與仿真計算與仿真 Matlab編程編程 (續(xù)續(xù)) - 函數(shù)申明與定義函數(shù)申明與定義 1: function mean,stdev = stat(x) 關(guān)鍵詞關(guān)鍵詞 輸出輸出 = (子子)函數(shù)名函數(shù)名 (輸入輸入) 7: function mean = avg(x,n) - 子函數(shù)調(diào)用子函數(shù)調(diào)用 4: mean = avg(x,n); MatlabMatlab計算與仿真計算與仿真 Matlab編程編程 (續(xù)續(xù)) - 函數(shù)的輸入輸出函數(shù)的輸入輸出 twosum.m two inputs, no output threes

4、um.m three inputs, one output addmult.m two inputs, two outputs - 1: function twosum(x,y) 2: % twosum Add two matrices 3: % and print the result 4: x+y MatlabMatlab計算與仿真計算與仿真 Matlab編程編程 (續(xù)續(xù)) 1: function s = threesum(x,y,z) 2: % threesum Add three variables 3: % and return the result 4: s = x+y+z; -

5、1: function s,p = addmult(x,y) 2: % addmult Compute sum and product 3: % of two matrices 4: s = x+y; 5: p = x*y; MatlabMatlab計算與仿真計算與仿真 Matlab編程編程 (續(xù)續(xù)) twosum的結(jié)果的結(jié)果 twosum(2,2) ans = 4 x = 1 2; y = 3 4; twosum(x,y) ans = 4 6 A = 1 2; 3 4; B = 5 6; 7 8; twosum(A,B); ans = 6 8 10 12 twosum(one,two) %

6、% 將字符串轉(zhuǎn)換成整數(shù)組將字符串轉(zhuǎn)換成整數(shù)組 ans = 227 229 212 MatlabMatlab計算與仿真計算與仿真 twosum的結(jié)果(續(xù)) clear x = 4; y = -2; twosum(1,2) ans = 3 x+y ans = 2 Matlab編程編程 (續(xù)續(xù)) disp(x y) 4 -2 who Your variables are: ans x y % 注意: x,y 沒有改變 MatlabMatlab計算與仿真計算與仿真 - threesum運行結(jié)果 a = threesum(1,2,3) a = 6 threesum(4,5,6) ans = 15 b=

7、threesum(7,8,9); 注：注：b的值為的值為24 Matlab編程編程 (續(xù)續(xù)) MatlabMatlab計算與仿真計算與仿真 - addmult運行結(jié)果 a,b = addmult(3,2) a = 5 b = 6 addmult(3,2) ans = 5 % 缺省只返回第一個輸出分量缺省只返回第一個輸出分量 Matlab編程編程 (續(xù)續(xù)) MatlabMatlab計算與仿真計算與仿真 -函數(shù)嵌套函數(shù)嵌套 function varScope1 x = 5; nestfun1 function nestfun1 nestfun2 function nestfun2 x = x +

8、1 end end end Matlab編程編程 (續(xù)續(xù)) MatlabMatlab計算與仿真計算與仿真 -函數(shù)嵌套函數(shù)嵌套(續(xù)續(xù)) function varScope2 x=; nestfun1 nestfun2 function nestfun1 x = 5; end function nestfun2 x = x + 1 end end % 必須在主程序中申明必須在主程序中申明 x,否則出錯否則出錯 Matlab編程編程 (續(xù)續(xù)) MatlabMatlab計算與仿真計算與仿真 Matlab編程編程 (續(xù)續(xù)) n 程序控制語句程序控制語句 - 選擇結(jié)構(gòu)選擇結(jié)構(gòu) 依據(jù)條件選擇執(zhí)行程序指令或依

9、據(jù)條件選擇執(zhí)行程序指令或模塊模塊 if 語句語句 % 條件選擇條件選擇 關(guān)鍵詞關(guān)鍵詞: if, else, 和和 elseif 基本格式基本格式: if logical_expression block of statements end MatlabMatlab計算與仿真計算與仿真 Matlab編程編程 (續(xù)續(xù)) if 語句一般形式語句一般形式 if logical_expression block of statements elseif logical_expression block of statements else block of statements end MatlabMa

10、tlab計算與仿真計算與仿真 Matlab編程編程 (續(xù)續(xù)) if 語句實例語句實例 if a 0 disp(a is negative); end if x 0 disp(x is positive); elseif x delta rold = r; r = 0.5*(rold + x/rold); end 1 2 newold old x rr r x MatlabMatlab計算與仿真計算與仿真 Matlab編程編程 (續(xù)續(xù)) while 語句實例語句實例: 循環(huán)中斷控制循環(huán)中斷控制 x = rand(1,10); k = 1; while k0.8 break end k = k + 1; end MatlabMatlab計算與仿真計算與仿真 Matlab編程編程 (續(xù)續(xù)) while 語句實例語句實例: 函數(shù)返回控制函數(shù)返回控制 x = rand(1,10); k = 1; while k0.8 return end k = k + 1; end MatlabMatlab計算與仿真計算與仿真 - 關(guān)于函數(shù)變量關(guān)于函數(shù)變量 輸入輸入(輸出輸出)變量查詢函數(shù)變量查詢函數(shù): nargin(nargout) 功能功能: 返回函數(shù)的輸入返回函數(shù)的輸入(輸出輸出)個數(shù)個數(shù) 應(yīng)用應(yīng)用: 根據(jù)變量個數(shù)根據(jù)變量個數(shù), 選取模塊執(zhí)行選取模塊執(zhí)行 function