matlab chapter 2
single element replacement
>> mat(i, j) = ___;
mat(:,N) or mat(M,:)
all elements in particular column or row
3D
array
reshape(mat,m,n,p)
changes M × N × P array to m × n × p
fliplr(mat)
changes first column to last, etc. (flips left-to-right)
flipud(mat)
changes first row to last, etc. (flips up-to-down)
row vector to column vector
r = 1:3; c = r'
random real numbers on the open interval (0,1)does not include 0 or 1
rand(N) or rand(M,N)
random integers on the closed interval [A,B] includes A and B
randi([A,B],N) or randi([A,B],M,N)
repelem(mat,m,n)
repeats each element of matrix 'mat' m × n times, forming a new mM × nN matrix
repmat(mat,m,n)
repeats matrix 'mat' m × n times, forming a new mM × nN matrix
mat(row, col)
reports element in arow,col position
mat(#)
reports element in position increasing columnwise
greater_than = mat > x
returns a logical array with true (1) or false (0) for each element
any(mat)
returns a row vector of logical 1s and 0s if any element in each column is nonzero or 'true'
all(mat)
returns a row vector of logical 1s and 0s if every element in each column is nonzero or 'true'
false(M,N,'logical')
returns an M×N logical matrix of 'false' 0s
true(M,N,'logical')
returns an M×N logical matrix of 'true' 1s
mat(greater_than)
returns elements of matrix mat > x
sum(greater_than)
returns number of elements of mat > x
find(mat > x)
returns position of elements of matrix mat > x using linear indexing
flip(mat)
row vectors l-to-r; col vectors u-to-d; matrix u-to-d;
Defined for vectors - equivalent to multiplying a row vector by a column vector
row*col = [a1 a2 a3] * [b1 b2 b3]' = a1b1 + a2b2 + a3b3
0D
scalar
[r, c] = size(mat)
stores length of each dimension
numel(mat)
total number of elements
Empty Matrix
vec = []
colon vector
vec = first:last vec = first:step:last
space filling vector
vec = linspace(first, last, num) vec = logspace(first, last, num)
"One" Matrix
vec = ones(N) vec = ones(M,N) M=column N=row
"Zero" Matrix
vec = zeros(N) vec = zeros(M,N) M=column N=row
space vector
vec= [1 2 3 4]
comma vector
vec= [1,2,3,4]
semicolon column vector
vec= [1; 2; 3; 4]
1D
vector
2D
matrix
length(mat)
largest of all dimensions
mat(M, end) or mat(end, N)
last element in particular column or row
matrix enter separated
mat = [1 2 3 4 5 6]
matrix using semicolon
mat = [1 2 3; 4 5 6; 7 8 9] mat = [1:3; 4:6; 7:9]
Row/Column replacement
mat(:, j) or mat(i, :) = ___;
Extend Matrix
mat(:, j+_) or mat(i+_, :) = ___;
Subset replacement
mat(i1:i2, j1:j2) = ___;
multiplication dot operator
mata .* matb = [a1 a2 a3] .* [b1 b2 = [a1b1 a2b2 a3b3] b3]
division dop operator
mata .* matb = [a1 a2 a3] ./ [b1 b2 = [a1/b1 a2/b2 a3/b3] b3]
exponent dot operator
mata .^ b = [a1 a2 a3]b = [a1b a2b a3b]
scalar multiplication
mata*b = [a1 a2 a3]*b = [a1b, a2b, a3b]
scalar division
mata/b = [a1 a2 a3]/b = [a1/b, a2/b, a3/b]
scalar addition
mata±b = [a1 a2 a3]±b = [a1±b, a2±b, a3±b]
