Create index between values

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Inna Pelloso
Inna Pelloso 2020-10-20
回答： Inna Pelloso 2020-10-21
Hi,
I have a 5 x 1 array, a = [ 0 1 0 2 0]. (this is a generalization of a larger problem)
I want create and index that fills all the values starting with 1, and ending at the last occurance of the number 2 (that does not have another 1 in between)?
I want to create b = [0 1 1 1 0].
I can do:
b = zeros(1,length(a))
b(strfind(a, [1]):strfind(a, [2])) = 1
That works for that specific case.
But, what if I have a = [ 0 1 0 2 0 2 1]? I want to create b = [0 1 1 1 1 1 0].
Any help woudl be appreciated! Thanks!
Inna

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采纳的回答

per isakson
per isakson 2020-10-20
Study this
%%
a = [0,1,0,2,0,2,1];
ixb = find( a==1, 1,'first'); % begin
ixe = find( a==2, 1,'last'); % end
%%
b = zeros(size(a));
b(ixb:ixe)=1;
b contains the result
>> b
b =
0 1 1 1 1 1 0
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per isakson
per isakson 2020-10-21
编辑：per isakson 2020-10-21
"the 'first' and 'last'" using Matlab includes a lot of searching and reading of the documentation.
per isakson
per isakson 2020-10-21
%%
a = [0,1,0,2,0,2,1,0,1,0,2];
chr = sprintf('%d',a);
[ix1,ix2] = regexp( chr, '1[^1]+2', 'start', 'end' );
%%
b = zeros(size(a));
for jj = 1 : numel(ix1)
b(ix1(jj):ix2(jj)) = 1;
end
and inspect b
>> b
b =
0 1 1 1 1 1 0 0 1 1 1
^
I think there is a mistake in your value of b ; a missing zero.
regexp() requires more than searching and reading the documentation.

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Inna Pelloso
Inna Pelloso 2020-10-21
Thank you! Really appreciate it.

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