1. 1. Lecture 4 Array addressing Eng. Mohamed Awni Electrical & Computer Engineering Dept.
2. 2. Agenda 2 Vector addressing (linear address) Matrix addressing (Subscripts address). Colon (:) Operator in addressing arrays. Adding elements to existing arrays. Deleting elements of an existing arrays. Exercise & Homework
3. 3. Vector Addressing (Linear address) is its position in the arrayAddress of an element in an array >> ve = [35 46 78 23 5 14 81 3 55] ve = 35 46 78 23 5 14 81 3 55 1 2 3 4 5 6 7 8 9 position or index of element ve(1) = 35 ve(2)= 46 . . . . ve(9)=55
4. 4. Subscript Address The address of an element in a matrix is denoted by the row index and the column index An element in the row number; i, and the column number; j, of the matrix p is p (i, j) The address of an element in the first row and the first column of the matrix is p(1,1) not p(0, 0). The matrix indices begin from 1 (not 0 (as in C)) The matrix indices must be positive integer Matrix addressing (Subscript address)
5. 5. 4 10 1 6 2 8 1.2 9 4 25 7.2 5 7 1 11 0 0.5 4 5 56 23 83 13 0 10 1 2 Rows (m) 3 4 5 Columns (n) 1 2 3 4 5 1 6 11 16 21 2 7 12 17 22 3 8 13 18 23 4 9 14 19 24 5 10 15 20 25 A = A (2,4) A (17) Matrix addressing
6. 6. Colon (:) Operator in addressing arrays Can be used to address a range of elements in a vector or a matrix A Colon (:) Addressing a range of vector elements
7. 7. 7 4 10 1 6 2 8 1.2 9 4 25 7.2 5 7 1 11 0 0.5 4 5 56 23 83 13 0 10 1 2 3 4 5 1 2 3 4 5 1 6 11 16 21 2 7 12 17 22 3 8 13 18 23 4 9 14 19 24 5 10 15 20 25 A = A(1:5,5) A(:,5) A(21:25) A(4:5,1:2) A([4 9;5 10]) Addressing a range of matrix elements Colon (:) Operator in addressing arrays A(:,n) Elements in all the rows of column n of the matrix A. (column) A(n,:) Elements in all the columns of row n of the matrix A (row) A(:,m:n) Elements in all the rows between columns m and n of matrix A A(:,2:3) A(2,:) A([2 7 12 17 22]) A(m:n,p:q) Elements in rows m through n and columns p through q of the matrix A
8. 8. Adding elements to existing arrays. An existing vector can be changed to have more elements An existing matrix can be changed to have more rows and/or columns 1 Adding elements to a vector A = 98 23 12 11 231 2 3 4 5 >> A(6)=12; >> A A = 98 23 12 11 23 6 12 240 7 8 A = 98 23 12 11 23 6 12 >> A(8)=24; >> A
9. 9. 2 Appending vector y to vector x >> z= [x,y] >> z= [x ; y] z = 98 23 12 11 23 11 24 15 16 17 1 2 3 4 5 6 7 8 9 10 y = 11 24 15 16 17 1 2 3 4 5 x = 98 23 12 11 231 2 3 4 5 Z = 98 23 12 11 231 3 5 7 9 11 24 15 16 17 2 4 6 8 10 Adding elements to existing arrays.
10. 10. 3 Adding elements to a matrix Adding new rows and/ or columns A = 98 23 12 111 3 5 7 11 24 15 16 2 4 6 8 >>A(3,:)=4:4:16 A = 98 23 12 111 4 7 10 11 24 15 16 2 5 8 11 4 8 12 16 3 6 9 12 >>A(:,5)= 4:2:6 A = 98 23 12 111 3 5 7 9 11 24 15 16 2 4 6 8 10 4 6 Adding new row Adding new column Adding elements to existing arrays.
11. 11. Appending a new matrix to the existing one >> C = [B A] >> B(5,5)= 333 Adding elements to existing arrays.
12. 12. Deleting elements of an existing arrays
13. 13. Exercise
14. 14. Homework