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Octave Matrices

Addition

Make two matrices addition. 
 
>> A = [1, 2, 3; 4, 5, 6]

   1   2   3
   4   5   6

>> B = [11, 22, 33; 44, 55, 66]

   11   22   33
   44   55   66

>> A + B

   12   24   36
   48   60   72

Range

Define vector range, default step is 1. 
 
>> v = 1:6

   1   2   3   4   5   6

>> v = 1:0.2:2

    1.0000    1.2000    1.4000    1.6000    1.8000    2.0000

Ones

Create a matrix with 1 at every column/row. 
 
>> ones(2,3)

   1   1   1
   1   1   1

Identity

Create an identity matrix (1 on diagonal). 
 
>> eye(4)

Diagonal Matrix

   1   0   0   0
   0   1   0   0
   0   0   1   0
   0   0   0   1

Transpose 

 
>> A = [1, 2, 3; 4, 5, 6]

   1   2
   3   4
   5   6

>> A'

   1   3   5
   2   4   6

Wise operations

Matrix wise operations, 
 
>> A

   1   2
   3   4
   5   6

>> B

   11   12
   13   14
   15   16

>> A .* B

   11   24
   39   56
   75   96

>> v = [1; 2; 3]

   1
   2
   3

>> 1 ./ v

   1.00000
   0.50000
   0.33333
Column wise maximum. 
 
>> A = magic(3)

   8   1   6
   3   5   7
   4   9   2

>> max (A,[],1) % column wise maximum

   8   9   7

>> max (A,[],2) % row wise maximum

   8
   7
   9

>> max(A(:)) % vector

   9

Find operatiions

Vector maximum value. 
 
>> a = [1 15 2 0.5]

    1   15    2    0.5

>> val = max(a)

     15

>> [val, ind] = max(a)

val =  15
ind =  2
Find indexes. 
 
>> A = magic(3)

   8   1   6
   3   5   7
   4   9   2

>> [r,c] = find (A >= 7)

r =
   1
   3
   2

c =
   1
   2
   3

>> A(2,3)
   
    7



  Last update: 249 days ago