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Matlab

Matlab. The language of technical computing. Outline. Introduction. C++ vs. Matlab. Functions. Graphing. Matrix. Image processing toolbox. Neural network toolbox. Menu. Introduction. Things we like about Matlab. Things we don’t like about Matlab. Help. Help command. Help svd.

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Matlab

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  1. Matlab The language of technical computing

  2. Outline • Introduction • C++ vs. Matlab • Functions • Graphing • Matrix • Image processing toolbox • Neural network toolbox • Menu

  3. Introduction • Things we like about Matlab • Things we don’t like about Matlab

  4. Help Help command Help svd

  5. C++ vs. Matlab int j; . for (j=1;j<23;j=j+2) { A[4][j]=3*j; } for i = 1:2:N for J = 1:N A(I,J) =(I+J-1); end end

  6. C++ vs. Matlab (cont.) int j; while (j<28) { …….; } while N> 0, E = E + F; F = A*F/N; N = N + 1; end

  7. C++ vs. Matlab (cont.) If (i==j) { A[i][j]=2; } else if (abs(i-j)!=1) { …….; } if i == j A(i,j) = 2; elseif abs(i-j) ~= 1 A(i,j) = -1; else A(i,j) = 0; end

  8. Index to an array can be zero. double, float , int… “;” is very important Index into matrix can’t be negative or zero. Don’t need to worry about the data type “;” not so important C++ vs. Matlab (cont.)

  9. Functions function [mean,stdev] = stat(x) n = length(x); mean = avg(x,n); stdev =… function mean = avg(x,n) mean = sum(x)/n; double* stat(double *x) { …….; return stdev; }

  10. Functions(cont.) void Matrix2Vector( ) { ……; ……; } function Matrix2Vector Av=A(1,:); for i=2:x Av=[Av A(i,:)]; end Av=Av';

  11. Functions(cont.) void AddF(int i); int main() { …… addF(i); } void AddF(int i) { i=i+1; } File name testFunR.m function testFun i=2; AddF(i); i function AddF(i) i=i+1; A function declaration cannot appear within a script M-file

  12. Graphing To make a graph of y = sin(t) on the interval t = 0 to t = 10 In file PlotTest.m t = 0:.3:10; y = sin(t); plot(t,y,’r’) ;

  13. Graphing(cont.) graphing the fuction z(x,y) = x exp( - x^2 - y^2) In file MeshTest.m [x,y] = meshgrid (-2:.2:2, -2:.2:2); z = x .* exp(-x.^2 - y.^2); mesh(z)

  14. Graphing(cont.) Multiple windows in one figure SubplotTest.m t = 0:.3:10; y = sin(t); z= cos(t); subplot(2,1,1); plot(t,y) ; subplot(2,1,2); plot(t,z);

  15. Graphing(cont.) Multiple windows in one figure SubplotTest.m t = 0:.3:10; y = sin(t); z= cos(t); subplot(1,2,1); plot(t,y) ; subplot(1,2,2); plot(t,z);

  16. Matrix >> A=[1 2 3;3 2 1] A = 1 2 3 3 2 1 >>b=A(1,:) b = 1 2 3 >> B=A' B = 1 3 2 2 3 1

  17. Matrix Manipulation • Singular value decomposition---[U,S,V]=svd(A) • Eigenvalues and eigenvectors---[V,D] = eig(A) • Orthogonal-triangular decomposition- [Q,R]=qr(A) • LU factorization --[L,U] = lu(A) • Matrix rank -- a=rank(A) • Condition number -- a=cond(A)

  18. Image Processing Toolbox • Read an image ---- I=imread(filename) • Display an image ---- imshow(I) • Write an image ---- imwrite(I, filename,FMT)

  19. Image Processing Toolbox(cont.) ImageRWD.m function ImageTest Itif=imread('image1.tif'); imwrite(Itif,'image1.bmp','bmp'); Ibmp=imread('image1.bmp'); subplot(1,2,1); imshow(Itif); subplot(1,2,2); imshow(Ibmp);

  20. Image Processing Toolbox(cont.) EdgeTest.m function EdgeTest Itif=imread('image1.tif'); B=edge(Itif,'canny'); subplot (1,2,1); imshow(Itif); subplot(1,2,2); imshow(B);

  21. Image Processing Toolbox(cont.) • Pixel values and statistics --corr2,imhist… • Image enhancement – histeq, medfilt2… • Linear filter -- conv2, filter2… • Image transform -- dct2, fft… • Binary image Op. --- dilate, erode…

  22. Neural Network • Feed-forward backpropagatoin • Hopfield Networks • Self-organizing maps • Radial Basis networks • ………………

  23. Neural Networks(cont.) • Create feed-forward NN • Net=newff([-1 2;0 5],[31],{‘tansig’,’purelin’},’traingd’); • Neural Model – tansig, logsig, purelin. • Training method –traingd, traingdm. • Training • [net,tr]=train(net,p,t) • net.trainParam.????; “show”, “lr”, “epochs”, “goal” • Simulation • A=sim(net,q);

  24. Menu function MenuDemo cell_list = {}; fig_number = 1; title_figure = 'Menu Demo'; cell_list{1,1} = {'Plot','PlotTest;'}; cell_list{1,2} = {'Mesh','MeshTest;'}; cell_list{1,3} = {'Image','ImageRWD;'}; cell_list{1,4} = {'Image Edge','EdgeTest;'}; cell_list{2,1} = {'????','PlotTest;'}; cell_list{2,2} = {'????','PlotTest;'}; cell_list{2,3} = {'????','PlotTest;'}; cell_list{2,4} = {'Exit',['disp(''Bye. To run again, type "menu".''); close(' num2str(fig_number) ');']}; show_window(cell_list,fig_number,title_figure,120,20,3);

  25. Menu (cont.) • cell_list{1,1} = {‘name',‘function;'}; • show_window(cell_list,fig_number,title_figure,x,y,z);

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