Basic MATLAB

Matlab

• Post-processer

• Graphics

• Analytical solution comparisons

Vectors>> a=[1 2 3 4]

a =

1 2 3 4

>> a'

ans =

1 2 3 4

Autofilling and addressing Vectors

> a=[1:0.2:3]'

a =

1.0000 1.2000 1.4000 1.6000 1.8000 2.0000 2.2000 2.4000 2.6000 2.8000 3.0000

>> a(2:3)ans =

1.2000 1.4000

xy Plots

>> x=[1 3 6 8 10];

>> y=[0 2 1 3 1];

>> plot(x,y)

Matrices>> b=[1 2 3 4;5 6 7 8]

b =

1 2 3 4 5 6 7 8

>> b'

ans =

1 5 2 6 3 7 4 8

Matrices

>> b=2.2*ones(4,4)

b =

2.2000 2.2000 2.2000 2.2000 2.2000 2.2000 2.2000 2.2000 2.2000 2.2000 2.2000 2.2000 2.2000 2.2000 2.2000 2.2000

Reshape>> a=[1:9]

a =

1 2 3 4 5 6 7 8 9

>> bsquare=reshape(a,3,3)

bsquare =

1 4 7 2 5 8 3 6 9

>>

Load and if

• a = load(‘filename’); (semicolon suppresses echo)

• if(1)

…

else

…

end

For

• for i = 1:10

• …

• end

Grad

[dhdx,dhdy]=gradient(h);

BMP Output

bsq=rand(100,100);

%bmp1 output

e(:,:,1)=1-bsq; %r e(:,:,2)=1-bsq; %g e(:,:,3)=ones(100,100); %b imwrite(e, 'junk.bmp','bmp');

image(imread('junk.bmp')) axis('equal')

Contours

• h=[…];

• contour(h)

• [C,H]=contour(h)

• Clabel(C,H)

Contours (load data, prepare matrix)

• rho=load('rho_frame0012_subs00.dat')• p_vector=rho/3• rows=100• columns=20

• for j=1:columns• j• for i=1:rows• p(i,j)=p_vector(j+(i-1)*columns); • • %Get rid of '0 pressure' solids that dominate pressure field• if p(i,j)==0• p(i,j)=NaN;• end• end• end

Contours

• [C,H]=contour(p)

• clabel(C,H)

• axis equal

Quiver (vector plots)

>> scale=10;

>> d=rand(100,4);

>> quiver(d(:,1),d(:,2),d(:,3),d(:,4),scale)

Quiver (and Quiver3)• uv_vector=load('u_frame0012_subs00.dat')

• rows=100• columns=20• for j=1:columns• j• for i=1:rows• u(i,j)=uv_vector(j+(i-1)*20,1); • v(i,j)=uv_vector(j+(i-1)*20,2);

• end• end

• hold on• quiver(u,v)

Streamline

• [Stream]= stream2(u,v,5,100)

• streamline(Stream)

Streamlines

• [Stream]= stream2(u,v,[1:20],100*ones(20,1));

• streamline(Stream)

• (This is for streamlines starting at y = 100 from x = 1 to 20 along the x axis. Different geometries will require different starting points.)