MATLAB: Some lements are not found using find in matlab array

finding an element in arrayismemeber

I used following code

a=0:0.001:3
ismember(2.8,a)
ans=1

later I changed

a=0:0.001:3
ismember(2.8,a)
ans=0

I then checked the element present at

a(2801)
ans=2.80000

then why ismemeber is not showing the element found in array when it actually exists?

You can use ismember to generate the logical indices. In the same order as a:

>> idx = ismember(a(:,1:2),b,'rows');
>> a(idx,:)
ans =
    3    7    0
    5   10    0

Or in the same order as b:

>> [~,idx] = ismember(b,a(:,1:2),'rows');
>> a(idx,:)
ans =
    5   10    0
    3    7    0

diff(a)==1

should do the job for you. It will show you where in a you have consecutive values..

a(diff(a)==1)

Gives the first value

p=find(diff(a)==1)
q=[p;p+1];
a(q)  % this gives all the pairs of consecutive numbers