User:Eml4507.s13.team7.wright
Section 12 M-files[edit]
Random integer matrix generator function a =randint(m,n,a,b)
if nargin <3, a=0; b=9; end a=floor((b-a+1)*rand(m,n))+a;
EDU>> randint(4,5)
ans =
8 6 9 9 4
9 0 9 4 9
1 2 1 8 7
9 5 9 1 9
Shows multiple outputs for a function function [mean,stdev]=stat(x)
[m n] = size(x) if m==1
m=n;
end mean =sum(x)/m; stdev=sqrt(sum(x.^2)/m-mean.^2);
EDU>> stat(4)
m = 1 n = 1 ans = 4
Storing E into memory EDU>> M=magic(6); E=zeros(6,50); for j=1:50 E(:,j)=eig(M^i); end
This code returns a zero of a function of one variable via the bisection method
function [b,steps]=bisectFEA(fun,x,tol)
if nargin <3, tol-eps;end trace=(nargout==2); if x~=0, dx =x/20;else, dx=1/20;end a=x-dx; fa=feval(fun,a); b=x+dx; fb=feval(fun,b);
while (fa>0)==(fb>0)
dx=2.0*dx; a=x-dx; fa=feval(fun,a) if (fa>0) ~= (fb>0), break, end b=x+dx; fb=feval(fun,b);
end if trace, steps=[a fa; b fb]; end
while abs(b-a) >2.0*tol*max(abs(b),1.0)
c= a+0.5*(b-a); fc=feval(fun,c);
if trace, steps=[steps; [c fc]]; end
if (fb>0)==(fc>0)
b=c; fb=fc;
else
a=c; fa=fc;
end
end
Section 13 text strings, error messages, input[edit]
EDU>> s='this is a test'
s =
this is a test
EDU>> disp('this message is hereby displayed') error('sorry, the matrix must be symmetric') this message is hereby displayed ??? sorry, the matrix must be symmetric
EDU>> iter=input('enter the number of iterations: ') enter the number of iterations: 3
iter =
3
Section 14: Managing M-files[edit]
EDU>> !ed rotate.m 'ed' is not recognized as an internal or external command, operable program or batch file.
Section 15: Comparing efficiency of algorithms: flops, tic and toc[edit]
Tic and toc before and after a statement gives EDU>> tic, any statement, toc
ans =
1
Elapsed time is 0.000838 seconds.
Section 16: Output format[edit]
No example
Section 17 Hardcopy[edit]
EDU>> diary brandon EDU>> ksfh;hr;ghwlrih;gwoi;r ??? Undefined function or variable 'ksfh'.
EDU>> yo ??? Undefined function or variable 'yo'.
EDU>> y=12;x=45; EDU>> diary off
Below is what appeared in the file named âBrandonâ
uiopen('C:\Users\Brandon\Documents\MATLAB\brandon',1) ksfh;hr;ghwlrih;gwoi;r {_??? Undefined function or variable 'ksfh'. }_ yo {_??? Undefined function or variable 'yo'. }_ uiopen('C:\Users\Brandon\Documents\MATLAB\brandon',1) y=12;x=45; uiopen('C:\Users\Brandon\Documents\MATLAB\brandon',1) diary off
Section 18. Graphics[edit]
Planar plots
EDU>> x=-1.5:.01:1.5; y=exp(-x.^2); plot(x,y)
3-D line plots
EDU>> t=.01:.01:20*pi; x=cos(t); y=sin(t); z=t.^3; plot3(x,y,z)
3-D mesh and surface plots
EDU>> [x,y]=meshgrid(-1:.2:2, -2:.2:2); z=exp(-x.^2-y.^2); mesh(z)
function [x,y,z]=torus(r,n,a)
if nargin <3, a=1; end if nargin <2, n=30; end if nargin <1, r=0.5; end theta=pi*(0:2:2*n)/n; phi=2*pi*(0:2:n)'/n; xx=(a+r*cos(phi))*cos(theta); yy=(a+r*cos(phi))*sin(theta); zz=r*sin(phi)*ones(size(theta)); if nargout == 0
surf(xx,yy,zz) ar=(a+r)/sqrt(2); axis([-ar,ar,-ar,ar,-ar,ar])
else
x=xx; y=yy ; z=zz;
end
Section 19: Sparse Matrix Computations[edit]
EDU>> F=floor(10*rand(6)); F=triu(tril(F,1),-1); EDU>> S=sparse(F)
S =
(1,1) 8 (2,1) 9 (1,2) 2 (2,2) 5 (3,2) 9 (2,3) 4 (3,3) 8 (4,3) 1 (3,4) 6 (5,4) 8 (4,5) 3 (5,5) 6 (6,5) 1 (6,6) 8
EDU>> F=full(S)
F =
8 2 0 0 0 0
9 5 4 0 0 0
0 9 8 6 0 0
0 0 1 0 3 0
0 0 0 8 6 0
0 0 0 0 1 8
EDU>> issparse(A) ??? Undefined function or variable 'A'.
EDU>> m=6; n=6; e=ones(n,1); d=-2*e; EDU>> T=spdiags([e,d,e],[-10,1],m,n)
T =
(1,2) -2 (2,3) -2 (3,4) -2 (4,5) -2 (5,6) -2
EDU>> i=[1 2 3 4 4 4]; j=[1 2 3 1 2 3]; s=[5 6 7 8 9 10]; EDU>> S=sparse(i,j,s,4,3), full(S)
S =
(1,1) 5 (4,1) 8 (2,2) 6 (4,2) 9 (3,3) 7 (4,3) 10
ans =
5 0 0
0 6 0
0 0 7
8 9 10
EDU>> n=6;e=floor(10*rand(n-1,1)); E=sparse(2:n,1:n-1,e,n,n)
E =
(2,1) 6 (3,2) 3 (4,3) 9 (6,5) 4