# How to find consecutive numbers

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Edward am 2 Apr. 2012
Beantwortet: Adil Sbai am 6 Mai 2017
So i have an array: a=[16 17 32 33 48 63 79 80 81 97 98 113 114 129 130]
how can i write a program to find where those consecutive numbers are? i've tried using a for loop but haven't really got anywhere.. Please note that at one point there is 3 consecutive numbers.. The idea is each of these numbers is an index of another array: value=[3 0 2 5 3 2 1 0 0 2 7 7 3 7 8]; all equally spaced, which is supposed to mean: realvalue=[30 25 3 2 100 27 73 78]; and im trying to get the array 'realvaue' from arrays 'a' and 'value'
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### Akzeptierte Antwort

Thomas am 2 Apr. 2012
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
or
p=find(diff(a)==1)
q=[p;p+1];
a(q) % this gives all the pairs of consecutive numbers
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ping pong am 13 Feb. 2014
Bearbeitet: ping pong am 13 Feb. 2014
working,its good

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### Weitere Antworten (2)

Andrei Bobrov am 2 Apr. 2012
Bearbeitet: Andrei Bobrov am 27 Sep. 2016
i1 = 1;
C{i1}=a(i1);
for j1 = 2:numel(a)
t = a(j1)-a(j1-1);
if t == 1
C{i1} = [C{i1} a(j1)];
else
i1 = i1 + 1;
C{i1} = a(j1);
end
end
OR
k= find(diff(a)==1);
k1 = [k;k+1];
idx = reshape(k1(k1~=intersect(k,k+1)),2,[]);
C = arrayfun(@(x)a(idx(1,x):idx(2,x)),1:size(idx,2),'un',0)
i1 = 1;
C(1)=1;
for j1 = 2:numel(a)
t = a(j1)-a(j1-1);
if t == 1
C(i1) = C(i1) + 1;
else
i1 = i1 + 1;
C(i1) = 1;
end
end
v = [3 0 2 5 3 2 1 0 0 2 7 7 3 7 8];
rv = str2double(mat2cell(sprintf('%d',v),1,C))
OR
k= find(diff(a)==1);
k1 = [k;k+1];
idx = reshape(k1(k1~=intersect(k,k+1)),2,[]);
id = sortrows([idx ones(2,1)*setdiff(1:numel(a),k1(:))].',1).';
C = diff(id)+1;
v = [3 0 2 5 3 2 1 0 0 2 7 7 3 7 8];
rv = str2double(mat2cell(sprintf('%d',v),1,C));
realvalue = accumarray(cumsum([true diff(a) ~= 1])',value',[],@(x)str2double(sprintf('%d',x')))
t = diff(a) == 1;
y = [t,false];
x = xor(y,[false,t]);
ii = cumsum(~(x|y) + y.*x);
out = accumarray(ii(:),value(:),[],@(z)10.^(numel(z)-1:-1:0)*z);
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Arun Badigannavar am 27 Sep. 2016
Does this work on simulink. parameters? what would be the best way to compare consecutive numbers in simulink dd?
yeungor am 27 Okt. 2016
Andrei definitely seems like a code golfer. Thanks for this, I'm using it to find linear regions in data.

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Adil Sbai am 6 Mai 2017
Call this function:
function bool = successive(a)
% Determines if all the numbers in a given input 1D array are successive
% integers.
%
assert((size(a,1)==1 || size(a,2)==1) && isa(a,'double'));
a = sort(a);
bool = (abs(max(a)-min(a))+1)==numel(a);
end
These are examples:
>> successive([-1 4 3 0 2 1])
ans =
1
>> successive([-1 4 3 -3 2 1])
ans =
0
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