How to check in MATLAB if a vector only contains zeros?

What is the "MATLAB-way" to check if a vector only contains zeros, so that it will be evaluated to a scalar rather than to a vector. If I run this code:

vector = zeros(1,10) %the "1" represents a function that returns a scalar if 1 && vector == 0 %this comparision won't work 'success' end 

I get the error:

??? Operands to the || and && operators must be convertible to logical scalar values.

5 Answers

Use all:

vector = zeros(1,10) if 1 && all(vector == 0) %this comparision will work 'success' end 

Since zeros are treated the same way as false, you don't need to use vector == 0, as ptomato suggests. ~any(vector) is the "MATLAB-way" to check for only zero values.

if 1 && ~any(vector) 'success' end 

Extending the problem to arrays, you'd have to use

array = zeros(5); if 1 && ~any(array(:)) 'success' end 

A bit late, but how about nnz (Number of Non-Zeros)?

if 1 && nnz(vector)==0 'success' end 

You can easily find out if any and how many entries in vector contain non-zero elements using the following:

vector = zeros(1, 10); nrNonZero = sum(vector~=0) 

vector~=0 returns an array of the same dimensions as vector containing zeros and ones, representing true and false, for the given statement. The variable nrNonZero then contains the number of non-zero elements in vector.

So, your code would then be

if (sum(vector~=0) == 0) 'success' end 

You can also do it using this:

if(boolFunCall() & ~vector) disp('True'); else disp('False'); end 

Just as Doresoom stated, your problem is in the use of && instead of &. Also, the ~ inverts all of the 1's and 0's thereby making a zero vector into a vector of 1's:

test = [0 0 0 0 0 0]; ~test ans = 1 1 1 1 1 1 1 test = [1 0 0 1 0 1 0 0 0]; ~test ans = 0 1 1 0 1 0 1 1 1