How to extract values from an array?

Hello all,

I have an array with values that repeat , is it possible to determine the start and end points of a particular value in the array. For example

array = [10 10 10 30 30 30 30 30 4 4 4 4 4 30 30 30 30 30 30 2 2 2 2 2 30 30 30 30];

the goal is to extract those values in between the 30s.

How can i go about this? Thanks

[Rik]

What would be the intended output? Perhaps this?

new_array=[4 2];

You can probably use most of the RunLength function Jan published on the file exchange.

[Daniel Adeniyi]

let me check out the RunLength function. i want to use the indices of the start and end 30 to extract the values in between to a new array. Thanks

[Rik]

If you want to extract the numbers, do you mean you want [4 2], or [4 4 4 4 4 2 2 2 2 2];? (or something else)

That is also probably important information if David's answer doesn't work for you.

[Daniel Adeniyi]

Yes you are right, I would want as output [4 4 4 4 4 2 2 2 2 2].

Answer 1

[Rik]

Using RunLength by Jan:

array = [10 10 10 30 30 30 30 30 4 4 4 4 4 30 30 30 30 30 30 2 2 2 2 2 30 30 30 30];

%first select only the parts between the first and last 30
new_array=array(find(array==30,1,'first'):find(array==30,1,'last'));
[B, N] = RunLength(new_array)

B = 1×5

30 4 30 2 30

N = 5×1

5 5 6 5 4

%remove the 30s
L=B==30;
B(L)=[];
N(L)=[];

%decode back to the normal array
new_array = RunLength(B, N)

new_array = 1×10

4 4 4 4 4 2 2 2 2 2

Answer 2

[David Hill]

a=num2str(yourArray==30);
a=a(a~=' ');
[s,f]=regexp(a,'[1]*');
new_array=[s,f];

[Daniel Adeniyi]

Is it possible to have an output such as [4 4 4 4 4 2 2 2 2 2] instead of their unique value.