While loop for the elements of an array

I have an array:

a=[1 1 1 1 1 1 1 10 1 1 1 1 1 1 12 1 1 1 1 3];

I want to make a while loop that does the following

enas=0;
while a(i)==1 % 
  enas=enas+1;
end

But I don't know how to express it in matlab. Can you help me please?

[Image Analyst]

It's recommended not to use i (the imaginary variable) as a variable name.

Answer 1

[Image Analyst]

Here's how you'd do it:

a=[1 1 1 1 1 1 1 10 1 1 1 1 1 1 12 1 1 1 1 3];
enas=0;
k = 1;
while a(k)==1 % 
  enas=enas+1
  k = k + 1
end

But here's how a real MATLAB programmer would do it:

enas = find(a~=1, 1, 'first')-1

[Giorgos Papakonstantinou]

Thank you Image. What if also have to count the in between ones?

[Image Analyst]

If you need to count the length of each stretch of 1's in your array, and if you have the Image Processing Toolbox, you'd do this:

measurements = regionprops(a==1, 'Area');
allLengths = [measurements.Area]; % Get lengths of all stretches of 1s.

If you don't have the Image Processing Toolbox, it's more difficult - let me know if you have that unfortunate case.

[Giorgos Papakonstantinou]

Unfortunately I don't. I just do:

a=[1 1 1 1 1 1 1 10 1 1 1 1 1 1 12 1 1 1 1 3]; 
enas = find(a~=1)-1
segments=zeros(length(enas),1);
segments(1,1)=enas(1);
segments(2:end,1)=diff(enas)-1;
segments

which a bit complicated but it does the job... If you have better ideas tell me. thank you!

Answer 2

[Jason Nicholson]

See the lines below. This will work.

 a=[1 1 1 1 1 1 1 10 1 1 1 1 1 1 12 1 1 1 1 3];
 i = 1;
 enas=0;
 while a(i)==1 % 
   enas=enas+1;
 i = i +1;
 end

[Giorgos Papakonstantinou]

thank you Jason!

[Giorgos Papakonstantinou]

I would like to count the ones in between. How I can I do that? In this example it would be 7 6 4.

[Matt Kindig]

This should do it:

b = [0, a, 0];   %ensure that ends are not 1
edges = find(b~=1);    %location elements that are not 1
spans = diff(edges)-1;  %distance between edges is span of 1's
enas = spans(spans~=0)  %should output 7 6 4

[Giorgos Papakonstantinou]

Suppose that I want find the edges of ones and of not ones. Suppose the array is:

a=[1 1 1 1 1 1 12 10 1 1 1 1 1 11 12 1 1 1 2 3]

a(1:6) -->area1 of ones
a(7:8) -->area1 of not ones
a(9:a13) -->area2 of ones
a(14:15)-->area2 of not ones
a(16:19)-->area3 of ones
a(20) -->area3 of not ones

and so on..