howto find out if a vector contains only one 1 and other are 0? or how to check if every entry is the same?

howto find out if a vector contains only one 1 and other are 0? or how to check if every entry is the same?

e.g. i need to check if a vector contains zeros except only one 1 like:

(0 0 0 0 1 0 0 0 0) -> tr开发者_运维知识库ue
(0 0 0 0 0 0 0 0 1) -> true
(0 0 0 0 2 0 0 0 0) -> false
(0 0 1 0 1 0 0 0 0) -> false

---

You can use logical indexing, assuming your vector is v: numel(v(v==1)) returns the number of elements equal to 1 in your vector.

In the same way, if you want to check if every value is the same you can use: numel(unique(v)) which returns the number of unique entries of v.

---

A slightly different solution:

v = [0 0 0 0 1 0 0 0 0];
TF = sum(v==1)==1           %# returns TRUE

This is especially useful if you want to apply it to all rows of a matrix:

M = [
    0 0 0 0 1 0 0 0 0 ;
    0 0 0 0 0 0 0 0 1 ;
    0 0 0 0 2 0 0 0 0 ;
    0 0 1 0 1 0 0 0 0 
];
TF = sum(M==1,2)==1

The result:

>> TF
TF =
     1
     1
     0
     0

---

The check for only zeroes could be achieved by extracting all unique elements from your variable:

u = unique (v)

You can then compare the result to zero and voila.

---

To check for a non-zero element, use the find function. If it finds only one index and that entry is one, your desired result is true. Otherwise it's false.

function bool = oneone(vector)
    num = find(vector);
    bool = isscalar(num) && vector(num)==1;
end

---

For all same entries, the diff function calculates the difference of subsequent elements. If any of the results are non-zero, your desired result is false.

function bool = allsame(vector)
    d = diff(vector);
    bool = ~any(d);
end