[Machine Learning] Octave Moving data around

Load data:

load featuresX.dat

who: Check how many variables in your current session:

who

whos: details about variables:

whos

Clear one variable:

clear M # delete the M variable

Clear all variables:

clear

Save the data into file:

save hello.mat v # save v variable into a file called hello.mat

Save as readable with -ascii:

save hello.txt v -ascii # save as text (ASCII)

Access one element in Metrix:

A = [1 2; 3 4; 5 6]
A(3, 2) # 6

Access one row/column:

A(2, :) # ':' means every element along that row/column

# 3 4

>> A(:, 2) # get second column data
"""
ans =

   2
   4
   6
"""

Access multi rows/columns:

>> A([1, 3], :) # get row 1 & 3
"""
ans =

   1   2
   5   6
"""

Assign one column/row:

>> A(:, 2) = [10; 11; 12] # assign second column
"""
A =

    1   10
    3   11
    5   12
"""

Append another column vector to right:

>> A = [A, [100; 101; 102]]
A =

     1    10   100
     3    11   101
     5    12   102

Put all element of A into a single vector:

>> A(:)
ans =

     1
     3
     5
    10
    11
    12
   100
   101
   102

Concat two matrixs:

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

   1   2
   3   4
   5   6

>> B = [10 11; 12 13; 14 15]
B =

   10   11
   12   13
   14   15

>> C = [A B]
C =

    1    2   10   11
    3    4   12   13
    5    6   14   15

>> D = [A; B]
D =

    1    2
    3    4
    5    6
   10   11
   12   13
   14   15