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Unit 9 檔案輸入與輸出

Unit 9 檔案輸入與輸出. 中華技術學院電子系 講師 蔡樸生. 開啟檔案. fopen : 開啟檔案 fid=fopen( ‘ filename ’ , ’ permission ’ ) ‘ r ’ : 只准讀取 (reading) ‘ w ’ : 只准寫入 (writing) fopen 傳回一個檔案辨識碼 fid=-1 : 表示檔案不存在 Ex : fid=fopen( ‘ a.m ’ , ’ r ’ ). 關閉檔案. status=fclose(fid); status=0 : 正常關閉檔案

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Unit 9 檔案輸入與輸出

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  1. Unit 9 檔案輸入與輸出 中華技術學院電子系 講師 蔡樸生

  2. 開啟檔案 • fopen : 開啟檔案 • fid=fopen(‘filename’,’permission’) • ‘r’ : 只准讀取(reading) • ‘w’: 只准寫入(writing) • fopen傳回一個檔案辨識碼 • fid=-1 : 表示檔案不存在 • Ex : fid=fopen(‘a.m’,’r’)

  3. 關閉檔案 • status=fclose(fid); • status=0 : 正常關閉檔案 • status=-1 : 無法順利關閉檔案 讀取ACSII檔案 • feof (fid) : 測試結束指標是否達到結束位置 • fgets (fid) / fgetl (fid) : 讀取一行 ASCII 碼 • fscanf (fid , format) : 讀取格式化資料

  4. EXAMPLE : • fid=fopen('ch9_1.m'); • while feof(fid)==0 • line=fgets(fid); line=fscanf(fid,’%s’) • disp(line); • End • fclose(fid) • % s : 字串 • % d : 10進制整數 • % g : 雙精制的浮點數

  5. EXAMPLE: 製作一ASCII檔案12 23 12 56 78… • fid=fopen('ch9_3.m'); • while feof(fid)==0 • char=fscanf(fid,'%d'); • disp(char); • end • fclose(fid);

  6. 寫入ASCII檔案 • fprintf(‘fid’,’format’,’y’) • fprintf(‘檔案名稱’,’寫入格式’,’變數1,…’) • format : 格式指定字串 • % e : 科學記號 • % f : 固定欄寬 • % g : 字串 • fprintf( ‘A unit circle has circumference %g\n\n’,2*pi) • fprintf( ‘X is %6.2f meter\n’,9.9)

  7. Homework x=1:10; y=[x;sqrt(x)]; fid=fopen('sqrt.dat','w'); fprintf(fid,'Table of Square Root:\n'); fprintf(fid,'%2.0f=>%10.6f\n',y); fclose(fid); 試將sin(t)正弦波分割成36等份,每一等 份為10度. 試將每一值寫入dsin.dat 中

  8. Unit 10 Symbolic Processing 中華技術學院電子系 講師 蔡樸生

  9. Algebraic and Math. Operator • syms : Create Symbolic Variables • expand : expands the expression by carrying out power • simplify : simplifies the expression E • factor : factors the expression E • >> syms x y • >> expand ((x+y)^3) • >> expand (sin(x+y)) • >> factor(x^2-1)

  10. Algebraic and Math. Operator • >> E1=x^2+5; • >> E2=y^3-2; • >> S1=E1+E2 : S1=x^2+3+y^3 • >> S2=E1*E2 : S2=(x^2+5)*(y^3-2) • >> expand(S2) • >> E3=x^3+2*x^2+5*x+10 • >> S3=E3/E1 • >> simplify(S3)

  11. Evaluating Expressions • subs(E,old,new): To replace old with a numeric value new in the expression E • ezplot(E,[xmin xmax]) • poly2sym([a,b,c…….],’v’) • >> syms x • >> E=x^2+6*x+7 • >> G=subs(E,x,2) • >> ezplot(E,[-2 6]) • >> ploy2sym([2,5,-3],’x’)

  12. Test Your Understanding (I) • Given the expressions: • Find the product E1*E2 and express it in its simplest form • Find the quotient E1/E2 and express it in its simplest form • Evaluate the sum E1+E2 at x=7.1

  13. Differentiation • syms n x y • diff(f(x,y),y,n) :對於f(x,y)中的 y 作偏微 n 次 Integration • int(f(x,y),y,a,b) : 對於f(x,y)由 a 到 b 作定積分

  14. Test Your Understanding (II) • Given that ,use MATLAB to find at x=0.2. • Given that ,use MATLAB to find • Given that ,use MATLAB to find • Use MATLAB to evaluate

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