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Matrix Transpose

Matrix Multiplication

Matrix Inverse If, A× B = I ,identity matrix Then, B= A -1 Identity matrix : 1 0 ... 0 0 0 1 ... 0 0 . . . . . . ... . 0 0 ...1 0 0 0 ... 0 1

X=

T UΣV

U and V are Orthonormal matrices

rxr diagonal matrix with r non-zero diagonal elements

1 0 0 0

0 0 0 4

X 0 3 0 0

0 0 0 0

2 0 0 0 = 0 0 0 1

U 0 1 0 0

∑ 1 0 0 0

0 4 0 0 0 0 0 0 3 0 0 0 x x -1 0 0 2.24 0 0.45 0 0 0 0 0 0

OPTIONAL R Code > M=matrix(c(1,0,0,0,0,0,0,4,0,3,0,0,0,0,0,0,2,0,0,0),nrow=4,ncol=5) > X=svd(M) > X$u > X$d > X$v > X$u%*%diag(X$d)%*%t(X$v)

T

V 1 0 0 1 0 0 0 0

0 0 0 0 0 0.89 1 0

Applications of SVD in image processing – closest rank-k approximation for a matrix X k

X

k

= ∑ u i Σi vi

T

i =1

– Each term in the summation expression above is called principal image

Original matrix (X) 1 0 0 0 2 0 0 3 0 0 0 0 0 0 0 0 4 0 0 0

1 0 0 0

0 0 0 4

X 0 3 0 0

k=1 0x 4x 0 0 1

0 0 0 0

2 0 0 0 = 0 0 0 1

Original size 4*5=20 bytes

U 0 1 0 0

T

∑ 1 0 0 0

0 4 0 0 0 0 0 0 3 0 0 0 x x -1 0 0 2.24 0 0.45 0 0 0 0 0 0

0 1 0 0 0=

0 0 0 0

0 0 0 4

0 0 0 0

0 0 0 0

0 0 0 0

V 1 0 0 1 0 0 0 0

0 0 0 0 0 0.89 1 0

Compressed size 4*1+1+1*5=10 bytes

k=2 0 0x 0 1 0 0 1 0 k=3 00 01 00 10

1x 0 0 0

k=4 00 01 00 10

1 0 0 0

40x 0 1 0 0 0= 0 0 03 0 0 1 0 0 0 0 0 0 0 4

40 0x 03 0 0 0 2.24

0 0 x -1 0

4 0 0 0

0 0 3 0 0 2.24 0 0

0 1 0 0 0.45 0

0 0 x 0 0

0 0 0.45 0

0 1 0

0 3 0 0

0 0= 0 0 0 0.89

1 0 0 0

0 1 0 0

0 0= 0 0 0 0.89 1 0

0 0 0 0

1 0 0 0

0 0 0 0

0 0 0 4

Compressed size 4*2+2+2*5=20 bytes

0 3 0 0

1 0 0 0

0 0 0 0

0 0 0 4

2 0 0 0

0 3 0 0

Compressed size 4*3+3+3*5=30 bytes

0 0 0 0

2 0 0 0

Compressed size 4*4+4+4*5=40 bytes

The image compression example in http://journal.batard.info/post/2009/04/08/svdfun-profit

• Original size = 384*384 bytes = 147,456 bytes • k=1: 384*1+1+1*384=769 bytes • k=10: 384*10+10+10*384=7,690 bytes • k=20: 384*20+20+20*384=15,380 bytes • k=50: 384*50+50+50*384=38,450 bytes • k=100: 384*100+100+100*384=76,900 bytes • k=200: 384*200+200+200*384=153,800 bytes

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