I am using Matlab.
I compare a zero array A with some other arrays (e.g. [1 1 0 0])
I write the following code:
A=[0 0 0 0];
if (A~=[1 1 0 0] & A~=[1 0 1 0] & A~=[1 1 0 1])
x=1;
else
x=0;
end
I expected to see that x=1 but the answer i get is x=0
what do i wrong ?
~= and & are element wise operators, so the expression
A~=[1 1 0 0] & A~=[1 0 1 0] & A~=[1 1 0 1]
where A = [0 0 0 0] produces the vector output:
[1 0 0 0]
An if statement evaluated on a vector does an implicit all, which in that case evaluates to false.
It's not exactly clear what you want, but if you want to make sure the vector A is not equal to any of [1 1 0 0], [1 0 1 0] or [1 1 0 1] then you need to do this:
x = ~isequal(A, [1 1 0 0]) && ~isequal(A, [1 0 1 0]) && ~isequal(A, [1 1 0 1])
The matlab equality operators compares array element-wise and returns true/false (logical 1/0) for each element. So when you have A = [1 1 0 0], B = [1 0 1 0] and you check for A == B, you don't get 'false' but instead you get [1 0 0 1].
If you want to check if the whole vectors A and B are equal you need to check if the condition
all(A==B)is true or not
I think you are looking to find exact match, so for that you may use this -
%%// If *ANY* of the element-wise comparisons are not-true, give me 1,
%%// otherwise give me 0. Thus, in other words, I am looking to find the
%%// exact match (element-wise) only, otherwise give me 1 as x.
if any(A~=[1 1 0 0] & A~=[1 0 1 0] & A~=[1 1 0 1])
x=1;
else
x=0;
end
Another way to put it would be -
%%// *ALL* elementwise comparisons must be satisfied, to give x as 0,
%%// otherwise give x as 1.
if all(A==[1 1 0 0] & A==[1 0 1 0] & A==[1 1 0 1])
x=0;
else
x=1;
end
x=1?