Boolean Operator
In
Matlab, there are four logical (aka boolean) operators:
| Boolean
operator: |
Meaning: |
|
& |
logical
AND |
|
| |
logical
OR |
|
~ |
logical
NOT (complement) |
|
xor |
exclusive
OR |
These
operators produce vectors or matrices of the same size as the operands,
with 1
when the condition is true,
and 0 when the condition is false.
Given
array x
= [0 7
3 5] and array y
= [2 8 7 0], these are some possible operations:
Operation:
Result:
n = x
&
y
n = [0
1
1 0]
m = ~(y
|
x)
m = [0
0
0 0]
p =
xor(x,
y)
p = [1
0
0 1]
Since
the output of the logical or boolean operations is a vector or matrix
with only 0
or 1
values, the output can be used as the index of a matrix to
extract appropriate
elements. For example, to see the elements of x
that satisfy both the
conditions (x<y) and (x<4), you can type
x((x<y)&(x<4)).
Operation:
Result:
x<y
ans =
[1 1
1
0]
x<4
ans =
[1 0
0
0]
q
=
x((x<y)&(x<4))
q
= [0 3]
Additionally to these boolean
operators, there are several useful built-in logical functions, such as:
| any |
true
if any element of a vector is true |
| all |
true if all elements of a vector are
true |
| exist |
true if the argument exists |
| isempty |
true for an empty matrix |
| isinf |
true for all infinite elements of a
matrix |
| isnan |
true for all elements of a matrix that
ara not-a-number |
| find |
finds indices of non-zero elements of
a matrix |
Relational
Operators
There
are six relational operators in Matlab:
| Relational
operator: |
Meaning: |
|
< |
less
than |
|
<= |
less
than or equal |
|
> |
greater
than |
|
>= |
greater
than or equal |
|
== |
equal
(possibility, not assignation) |
|
~= |
not
equal |
These operations result in a vector of matrix
of the
same size as the operands, with 1 when the relation is true, and 0 when
it’s
false.
Given arrays x
= [0 7
3 5] and y
= [2 8 7 0], these are some possible relational operations:
Operation:
Result:
k =
x<y
k = [1 1
1
0]
k
= x <= y
k = [1 1
1
0]
k
= x == y
k = [0 0
0
0]
Although these operations are usually used in
conditional statements such as if-else
to branch out to different cases, they
can be used to do very complex matrix manipulation. For example x
= y(y
>
0.45) finds all the elements of vector y
such that yi
> 0.45 and
stores them in vector x.
These operations can be combined with boolean
operators, too.
|
