MATLAB by rudra pratap

3.1 Matrices and Vectors
65
3.1 Matrices and Vectors
3.1.1 Input
A matrix is entered row-wise, with consecutive elements of a row separated by a
space or a comma, and the rows separated by semicolons or carriage returns. The
entire matrix must be enclosed within square brackets . Elements of the matrix may
be real numbers, complex numbers, or valid MATLAB expressions. 2
Examples:
Matrix
A=[
B =
[ 2x
5i
2
9 ]
ln x + sin y
3 + 2i
Special cases: Vectors and scalars
MATLAB input command
A = [1 2 5; 3 9 0]
B [2*x log (x)+sin(y) ; 5i 3+2i]
(see the note in the margin.)
• A vector is a special case of a matrix, with just one row or one column. It is
entered the same way as a matrix.
Examples: u = [1 3 9] produces a row vector, and
v = [1; 3; 9] produces a column vector.
• A scalar does not need brackets.
Example: g = 9. 81;
• Square brackets with no elements between them create a null matrix.
Example: X = []. (See Fig. 3.1 for a more useful example) .
Fo r on-line help' ·
•tv:P8:,:
hep
• "· ""
For the matrix
B command to
work, variables
x and y must be
predefined, e.g.,
x=l ; y=2 ;, etc.
Continuation
If it is not possible to type the entire input on the same line, then use three consecutive
periods ( .. . ) to signal continuation and continue the input on the next line.
The three periods are called an ellipsis. For example,
A = [1/3 5.55*sin (x) 9.35 0.097 ; . . .
3/ (x+2*log(x) ) 3 0 6.555 ; .. .
(5*x-23)/55 x-3 x*sin(x) sqrt(3)] ;
produces the intended 3 x 4 matrix A (provided, of course, x has been assigned
a value before) . A matrix can also be entered across multiple lines using carriage
returns at the end of each row. In this case, the semicolons and ellipses at the end
of each row may be omitted. Thus, the following three commands are equivalent:
A = [1 3 9; 5 10 15; 0 o -5] ;
A = [1 3 9
5 10 15
0 0 -5] ;
A [1 3 9; 5 10 ...
15 ; 0 0 -5] ;
2 The box on the right lets you know that you can learn more about this topic from M.A'T'LAB's
on-line help, on the help topic called elmat (for elementary matrix manipulations) .