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MATLAB Variables
Objective: To study data types, constant and variable, character, operators, assignment statement. To consider vectors and matrices commands to operate on vectors and matrices, matrices manipulation.
Variables: MATLAB variable is a region of memory containing an area which is known by the user-specified name.
These are of two types:
- double: – 64 bit (10^-308 to 10^308 with 15 to 16 significant decimal digits).
e.g: var=10.5 //Real value var=10i , var=-4j //Imaginary value var=10+10i
- char: – 16 bit (-32768-32767)
e.g: var='This is a character string';
Initialization of a variable:
- Assignment statement: It is simplest and used for small arrays.
      Var=expression;
Where var is name and expression are a scaler constant, an array or a combination of constraints, other variables, and mathematical operations.
The number of elements in every row must be same. Also, the number of elements in every column must be the same.
>> var= [3.4] //creates a 1x1 array with value 3.4 var = 3.4000 >> var= [1.0 2.0 3.0] // creates a 1x3 array with value [1 2 3] var=1 2 3 >> var= [1.0;2.0;3.0] // creates a 3x1 array var = 1 2 3 >> var= [1,2,3;4,5,6] //creates a 2x3 array var = 1 2 3 4 5 6 >> var= [1,2,3 4,5,6] //creates a 2x3 array var = 1 2 3 4 5 6 >> var= [] //creates an empty array var = [] >> var1= [0 1+7] var1 = 0 8 >> var2=[var1(2) 7 var1] var2 = 8 7 0 8 >> var3(2,3) =5 var3 = 0 0 0 0 0 5 >> var3(3,3) =6 var3 =0 0 0 0 0 5 0 0 6
- Shortcut expressions:
>> x= [1:2:10] x = 1 3 5 7 9
Shortcuts can be combined with the transpose operator (‘) to initialize column vectors.
>> f= [1:4]' f =1 2 3 4 >> g=[1:4] g =1 2 3 4 >> h=[g',g'] h =1 1 2 2 3 3 4 4
- Built in functions:
Zeros:
>> a=zeros (2) a =0 0 0 0 >> b=zeros (2,3) b = 0 0 0 0 0 0 >> c= [1,2;3,4] c =1 2 3 4 >> d=zeros(size(c)) d = 0 0 0 0
Ones: 0’s are replaced by 1’s
>> f=ones (4) f = 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
Eyes: to generate arrays containing identity matrices in which all on-diagonal element is 1 while all off-diagonal element is 0.
>> e=eye(4) e = 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1
- Keyboard input:input funcn
- var=input (‘enter a input value’)
- enter a input value
- var=input (‘enter data’,’s’)
- enter data 3
var =3
- Multidimensional array
- c(:,:,1) =[1 2 3;4 5 6]
- c = Â Â Â 1 Â Â Â 2 Â Â Â 3
   4    5    6 - c(:,:,2) = 7    8    9
   10    11    12
- STORING MULTIDIMENSIONAL ARRAY IN MEMORY
•Eg: a= [1 2 3;4 5 6;7 8 9;10 11 12] a = 1 2 3 4 5 6 7 8 9 10 11 12
- Subarray
•arr= [1 2 3;-2 -3 -4;3 4 5] arr = 1 2 3 -2 -3 -4 3 4 5 arr1(1,:)=[1 2 3] •arr1 = 1 2 3
- End func:
•arr=[1 2 3 4 5 6 7 8]; •>> arr(5:end) ans = 5 6 7 8 •>> arr(1:2,[1,4])=[20 21 ;22 23] arr = 20 2 3 21 5 6 7 8 22 0 0 23 0 0 0 0 •>> arr=[1 2 3 4 ;5 6 7 8;9 10 11 12]; •>> arr(1:2,1:2)=1 arr = 1 1 3 4 1 1 7 8 9 10 11 12
- Predefined specific values:
- pi: It contains values up to 15 significant digits
- inf: infinity
- nan: not a number
- clock: current date & time in the form of 6 element vector containing
year, month, datemin and second - date: current date in a character string format eg:24-Jan-2019
- eps:Esiton i.e smallest difference b/w two no’s
- ans: It used to store the result of an expression
- Displaying Output Data:
- Disp fn: It accepts an array of arguments & shows the value of the array in the command
window str=['the value of pi='num2str(pi)]; disp(str);
- Disp fn: It accepts an array of arguments & shows the value of the array in the command
- Formatted Output Function With fprintf Function:
- Display one or more values together with related text & lets the programmer to control the way the display value appears
- Syntax: fprintf(format,data);
- Eg:fprintf(‘the value of pi=%fn’,pi);
fprintf(‘the value of pi=%dn’,pi);
fprintf(‘the value of pi=%en’,pi);
- Scalar Operations:
•E.g.: =2^ ((8+2)/5) =26(10/5) =2^2 =4
- Array Operations:
z=1 >> z z =1 2 3 4 >> y=-1 y = -1 >> y y =-1 3 -2 0 >> y+z ans = 0 5 1 4
- Matrix Operation based on Linear Algebra:
| Operations | Matlab Form | Comments |
|---|---|---|
| Array Addition | a+b | Array & matrix addition are identical |
| Array Subtraction | a-b | Array & matrix subtraction are identical |
| Array Multiplication | a.*b | Array multiplication element by element multiplication of a & b |
| Matrix Multiplication | a*b | For matrix multiplication no of the column in matrix a=no of column of matrix b |
| Array Right Division | a./b | Element by element division of a & b |
| Array Left Division | a.b | Element by element division of a & b with in the Nr. |
| Matrix Right Division | a/b | a* inv(b) where inv represent inverse |
| Matrix Left Division | ab | inv(a)*b |
| Array Exponential | a.^b | Element by element exponential of a & b i.e a( i , j) ^ b( i , j) |
Next TopicMATLAB Operations on Matrices