Graphics Programs Reference
InDepth Information
Logical operators
&
AND

OR
~
NOT
xor
EXCLUSIVE OR
any
True if any element is nonzero
all
True if all elements are nonzero
We continue the previous example and use
find
to plot the part of
the peaks function that lies between
y
= 20 and
y
= 40:
clf
ind = find(20<=y & y<=40);
plot(x,y,x(ind),y(ind),'o')
grid
When used with one output argument,
find
assumes that the input is
a vector. When the input is a matrix
find
first strings out the elements
as a single column vector and returns the corresponding indices. As an
example we consider the spiral matrix:
>> s = spiral(3)
s=
7 8 9
6 1 2
5 4 3
We find the elements of
s
less than 6:
>> s<6
ans =
0
0
0
0
1
1
1
1
1
>> find(s<6)
ans =
3
5
6
8
9
The result of
find
is a vector of indices of
s
counted down the first col
umn, then the second, and then the third. The following example shows
how the results of the find command can be used to extract elements
from a matrix that satisfy a logical test: