How to eliminate the junk values in the index

a = (1,3,4,6,8,9,0,5,4,)

b = (3)

c = (4,56,7,8,5,1)

a, b, c are saved in .vec extension

a = load ('numbers.vec');

b = load ('numbers1.vec');

c = load ('numbers2.vec');

value = period_fun (2,1,1);

The above code is just for information

my actual isssue is here

idx = find (period_fun == 1.1); % suppose your are looking for 1.1 in period_fun

[a, b, c] = ind2sub (size (period_fun), idx);

I am trying to get the index of a, b, c

So when i run it. sometimes a carries more than one index

Suppose for eg for the code when i run it it get

a = 1,000 4,000

Expected answer is 1,000 but why did 4.0000 come?

How can we eliminate the other values?

Please help me out

Answer 1

[Steven Lord]

x = [1 2 3 2 3 4 2];
locations = find(x == 2)

The output of this find call has three elements (2, 4, and 7) since x contains three instances of the number 2 at locations 2, 4, and 7. If you only want to find the first or last instances find accepts options to do this.

firstTwo = find(x == 2, 1, 'first') % Find the first 1 instances of 2
lastTwoTwos = find(x == 2, 2, 'last') % Find the last 2 instances of 2

As a side note, testing for exact equality with floating-point values like 1.1 could give you results you don't expect (see especially the first example in the common problems section on that page.) In that scenario you probably want to compare with a tolerance or perhaps use the ismembertol function.

x = 0:0.1:1;
find(x == 0.3) % Not found
find(abs(x-0.3) <= eps) % found element 4 in x

[Image Analyst]

But is that the right eps? The value of eps depends on the range of the numbers you're considering:

>> eps

ans =

2.22044604925031e-16

>> eps(1)

ans =

2.22044604925031e-16

>> eps(100)

ans =

1.4210854715202e-14

>> eps(900)

ans =

1.13686837721616e-13

>> eps(mean(x))

ans =

1.11022302462516e-16

So what is the right argument to pass in to eps()? Not sure, so maybe using ismembertol() makes things more certain.