Moving Data (Octave)

Matrices
1. A = [1 2; 3 4; 5 6]
$A=\begin{pmatrix} 1 & 2 \\ 3 & 4 \\ 5 & 6 \end{pmatrix}$

2. size(A) size of matrix
$\begin{matrix} 3 & 2 \end{matrix}$

3. size(A,1) number of rows
ans = 3

4. size(A,2) number of columns
ans = 2

5. A(3,2) $A_{32}$
ans = 6

6. A(2,:) every element along row 2
$\begin{pmatrix} 3 & 4 \end{pmatrix}$

7. A(:,1) every element along column 1
$\begin{pmatrix} 1\\ 3\\ 5 \end{pmatrix}$

8. A([1 3],:) every element along rows 1 and 3
$\begin{pmatrix} 1 & 2\\ 5 & 6 \end{pmatrix}$

9. A(:,2) = [10; 11; 12] replace column 2 with new elements
$\begin{pmatrix} 1 & 10 \\ 3 & 11 \\ 5 & 12 \end{pmatrix}$

10. A = [A, [100; 101; 102]] append new column vector to the right
$\begin{pmatrix} 1 & 10 & 100 \\ 3 & 11 & 101\\ 5 & 12 & 102 \end{pmatrix}$

11. A(:) put all elements of A into a single vector
$\begin{pmatrix} 1\\ 3\\ 5\\ 10\\ 11\\ 12\\ 100\\ 101\\ 102 \end{pmatrix}$

12. A = [1 2; 3 4; 5 6]
B = [11 12; 13 14; 15 16]
C = [A B] concatenating A and B
$C=\begin{pmatrix} 1 & 2 & 11 & 12 \\ 3 & 4 & 13 & 14\\ 5 & 6 & 15 & 16 \end{pmatrix}$

13. C = [A; B] putting A on top of B
$C=\begin{pmatrix} 1 & 2 \\ 3 & 4 \\ 5 & 6 \\ 11 & 12 \\ 13 & 14 \\ 15 & 16 \end{pmatrix}$

14. v = [1 2 3 4]
$v=\begin{pmatrix} 1 & 2 & 3 & 4 \end{pmatrix}$

15. length(v) length of vector v
ans = 4

Loading files
1. path: pwd shows where Octave location is

2. change directory: cd '/Users/eugene/desktop'

3. list files: ls

4. load files: load featuresfile.dat

5. list particular file: featuresfile

6. check saved variables: who

7. check saved variables (detailed view): whos

8. clear particular variable: clear featuresfile

9. clear all: clear

10. restrict particular variable: v = featuresfile(1:10) only first 10 elements from featuresfile

11. save variable into file: save testfile.mat v variable v is saved into testfile.mat

12. save variable into file: save testfile.txt v -ascii variable v is saved into text file