Page 35 - Basics of MATLAB and Beyond

Logical operators & AND
| OR
~ NOT
xor EXCLUSIVE OR
any True if any element is non-zero
all True if all elements are non-zero
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:

c 2000 by CRC Press LLC