MATLAB: 3>2>1 returns logical 0

logical?

When I run 3>2>1 it returns logical 0 (false). Sorry if its a basic question but I can't understand how this is not true.

Best Answer

The basic problem is that you are attempting two logical relations simultaneously: MATLAB's relational operators are binary operators, so they only support one comparison at once. In summary:

X<A<Y     % is NOT valid for comparing A against X and Y
X<A & A<Y % This compares A with both X and Y

In MATLAB logical relational operators follow the standard rules of operator precedence. Look at this example carefully:

>> 3<4<2
ans =
     1

The output is true, so does this mean that 4<2 ? Of course not, we just have to remember the operator precedence rules, just like in high school. This is evaluated according to those rules as:

>> (3<4)<2
ans =
     1

where

>> 3<4
ans =
     1

So 3<4<2 is actually equivalent to 1<2, which is of course very true:

>> 1<2
ans =
      1

Related Solutions

MATLAB: & operator without if

The & operator is an elementwise operator. Just like the + operator will add corresponding elements of its inputs when given two vectors of the same size:

x = [1 2 3];
y = [4 5 6];
z = x + y % z(1) = x(1) + y(1), z(2) = x(2) + y(2), z(3) = x(3) + y(3)

The & operator will take the and of the corresponding elements of its inputs.

a = [true false true];
b = [true true false];
c = a & b; % c(1) = a(1) & b(1), c(2) = a(2) & b(2), c(3) = a(3) & b(3)

The & operator with two scalars as input returns true if both its inputs are non-zero and false otherwise.

[ true &  true; ... % true
  true & false; ... % false
 false &  true; ... % false
 false & false]     % false

MATLAB: Two different ways of expressing the same logical condition lead to two different results ??