3. Matrices
3.2 Locating elements of matrices
3.4 Determining the size of a matrix
3.6 Creating matrices with short-hand methods
3.7 Checking the status of matrices
3.8 Clearing and emptying matrices
3.9 Practicing with matrices
Code 3.1.1:
A = [1, 2, 3, 4, 5, 6]
Output 3.1.1:
A =
1 2 3 4 5 6
Code 3.1.2:
B = [4, .8, -.12, 0, -24]
Output 3.1.2:
B =
4.0000 0.8000 -0.1200 0 -24.0000
Code 3.1.3:
C = [4 .8 -.12 0 -24]
Output 3.1.3:
C =
4.0000 0.8000 -0.1200 0 -24.0000
Code 3.1.4:
D = [1 2; 3 4; 5 6]
Output 3.1.4:
D =
1 2
3 4
5 6
Code 3.1.5:
D = [1 2; 3 4; 5 6];
Output 3.1.5:
>>
Code 3.1.6:
E = [1 2 3; 4 5; 6 7 8];
Output 3.1.6:
??? Error using ==> vertcat
All rows in the bracketed expression must have the same
number of columns.
Code 3.2.1:
D(1,1)
Output 3.2.1:
ans =
1
Code 3.2.2:
D(2,2)
Output 3.2.2:
ans =
4
Code 3.2.2:
D(:,1)
Output 3.2.2:
ans =
1
3
5
Code 3.2.3:
D(:,2)
Output 3.2.3:
ans =
2
4
6
Code 3.2.4:
D(1,:)
Output 3.2.4:
ans =
1 2
Code 3.2.5:
E = [1 2 3 4; 5 6 7 8; 9 10 11 12]
Output 3.2.5:
E =
1 2 3 4
5 6 7 8
9 10 11 12
Code 3.2.6:
E(end,2)
Output 3.2.6:
ans =
10
Code 3.2.7:
E(2,end)
Output 3.2.7:
ans =
8
Code 3.2.8:
E(2,end-1)
Output 3.2.8:
ans =
7
Code 3.3.1:
F = [10 11 12];
G = [13 14 15];
H = [F;G]
Output 3.3.1:
H =
10 11 12
13 14 15
Code 3.3.2:
H = [F G]
Output 3.3.2:
H =
10 11 12 13 14 15
I = [20 21 22 23 24 25 26];
Code 3.3.3:
J = [H;I]
Output 3.3.3:
??? Error using ==> vertcat
All rows in the bracketed expression must have the same
number of columns.
Code 3.3.4:
K = [H I]
Output 3.3.4:
K =
10 11 12 13 14 15 20 21 22 23 24 25 26
Code 3.4.1:
size(I)
Output 3.4.1:
ans =
1 7
Code 3.4.2:
sz_K = size(K)
Output 3.4.2:
sz_K =
1 17
Code 3.4.3:
[rows columns] = size(K)
Output 3.4.3:
rows =
1
columns =
17
Code 3.4.4:
JJ = [1:4;5:8]
Output 3.4.4:
JJ =
1 2 3 4
5 6 7 8
Code 3.4.5:
size (JJ)
Output 3.4.5:
ans =
2 4
Code 3.4.6:
length(JJ)
Output 3.4.6:
ans =
4
Code 3.4.7:
KK = [1 5; 2 6; 3 7; 4 8]
Output 3.4.7:
ans =
1 5
2 6
3 7
4 8
Code 3.4.8:
length(KK)
Output 3.4.8:
ans =
4
Code 3.5.1:
J = [1 2 3 4];
K = [5;6;7;8]
Output 3.5.1:
K =
5
6
7
8
Code 3.5.2:
L = [J;K]
Output 3.5.2:
??? Error using ==> vertcat
All rows in the bracketed expression must have the same
number of columns.
Code 3.5.3:
K’
Output 3.5.3:
ans =
5 6 7 8
Code 3.5.4:
L = [J;K']
Output 3.5.4:
L =
1 2 3 4
5 6 7 8
Code 3.5.4:
L'
Output 3.5.4:
ans =
1 5
2 6
3 7
4 8
Code 3.6.1:
M = [1 2 3 4 5 6];
Code 3.6.2:
M = [1:6]
Output 3.6.2:
M =
1 2 3 4 5 6
Code 3.6.3:
MM = [1:.5:6]
Output 3.6.3:
MM =
1.0000 1.5000 2.0000 2.5000 3.0000 3.5000 4.0000 4.5000 5.0000 5.5000 6.0000
Code 3.6.4:
MM'
Output 3.6.4:
ans =
1.0000
1.5000
2.0000
2.5000
3.0000
3.5000
4.0000
4.5000
5.0000
5.5000
6.0000
Code 3.6.5:
Descending_Matrix = [5:-2:-7]
Output 3.6.5:
Descending_Matrix =
5 3 1 -1 -3 -5 -7
Code 3.6.6:
s = [5:-6:-3]
Output 3.6.6:
s =
5 -1
Code 3.6.7:
s = linspace(5,-3,10);
s’
Output 3.6.7:
ans =
5.0000
4.1111
3.2222
2.3333
1.4444
0.5556
-0.3333
-1.2222
-2.1111
-3.0000
Code 3.6.8:
help logspace
Output 3.6.8:
LOGSPACE Logarithmically spaced vector.
LOGSPACE(X1, X2) generates a row vector of 50 logarithmically
equally spaced points between decades 10^X1 and 10^X2. If X2
is pi, then the points are between 10^X1 and pi.
LOGSPACE(X1, X2, N) generates N points.
For N < 2, LOGSPACE returns 10^X2.
See also LINSPACE, :.
Code 3.6.9:
sss = logspace(1,2,5)
Output 3.6.9:
sss =
10.0000 17.7828 31.6228 56.2341 100.0000
Code 3.7.1:
who
Output 3.7.1:
Your variables are:
Descending_Matrix JJ lg sss
II ans s
Code 3.7.2:
whos
Output 3.7.2:
Name Size Bytes Class
Descending_Matrix 1x7 56 double array
II 2x4 64 double array
JJ 4x2 64 double array
ans 1x2 16 double array
lg 1x5 40 double array
s 1x10 80 double array
sss 1x5 40 double array
Grand total is 45 elements using 360 bytes
Code 3.8.1:
clear s
whos
Output 3.8.1:
Name Size Bytes Class
Descending_Matrix 1x7 56 double array
II 2x4 64 double array
JJ 4x2 64 double array
ans 1x2 16 double array
lg 1x5 40 double array
sss 1x5 40 double array
Grand total is 35 elements using 280 bytes
Code 3.8.2:
sss
size(sss)
sss(end-1:end) = []
size(sss)
Output 3.8.2:
sss =
10.0000 17.7828 31.6228 56.2341 100.0000
ans =
1 5
ans =
10.0000 17.7828 31.6228
ans =
1 3
Code 3.8.3:
sss = []
size(sss)
Output 3.8.3:
sss =
[]
ans =
0 0
Code 3.8.4:
matrix_to_be_added_to = []
matrix_to_be_added_to =[matrix_to_be_added_to; 1]
matrix_to_be_added_to =[matrix_to_be_added_to; 2]
matrix_to_be_added_to =[matrix_to_be_added_to; 3]
matrix_to_be_added_to =[matrix_to_be_added_to; 4]
Output 3.8.4:
matrix_to_be_added_to =
[]
matrix_to_be_added_to =
1
matrix_to_be_added_to =
1
2
matrix_to_be_added_to =
1
2
3
matrix_to_be_added_to =
1
2
3
4