Introduction to MATLAB - Continuous and Discrete Time Signals and Systems - page 831

E.2 Entering data i nto M ATLAB
Data can be entered in the M ATLAB as a scalar quantity, a row or column vector,
and a multidimensional array. In each case, both real and complex numbers can
be entered. As required in other high-level languages, there is no need to declare
the type of a variable before assigning data to it. For example, variable a can
be assigned the value (6 + j8) by typing the following command:
>>a=6+j*8
On the execution of the above command, M ATLAB returns the following
answer:
a = 6.0000 + 8.0000i
In the above command, we did not allocate any value to j , yet M ATLAB
recognized it as a complex operator with value j 2 = 1 . There is a whole range
of special words that are used by M ATLAB either as the name of functions or
variables. These include pi , i , j , Inf , NaN , sin , cos , tan , exp , and rem .
Type help elfun to list the names that are used by M ATLAB to specify the
built-in functions and variables. The value of any of these special words can be
changed by assigning a new value to it. For example,
>> sin = 1
allocates the value of 1 to the variable sin . The M ATLAB definition of
the trigonometric sine is overwritten by our command. To check the cur-
rent status of the runtime environment of M ATLAB , type whos at the
prompt:
>> whos
M ATLAB returns the following answer:
Name Size Bytes Class
a 1x1 16 double array (complex)
sin 1x1 8 double array
Grand total is 2 elements using 24 bytes
Alternatively, the command who can also be used to list the name of defined
variables in the M ATLAB runtime environment. The command who does not
provide additional details such as the size and class of each variable. In the
preceding discussions, we overwrote the sin function and allocated a value of
1 to it. Consequently, we cannot access the M ATLAB built-in function sin
to evaluate the sine of an angle. To clear our definition of sin , we can use the
following command:
>> clear sin