# Champernowne Constant loop help

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Nguyen Huy on 15 May 2021
Edited: Jonas on 16 May 2021
%i have Champernowne Constant is a real number whose digits in decimal representation come from the concatenation of all consecutive positive integers starting from 1. ex:'12345678910111213....'
%my job is return array vy contain nth digit from Champernowne Constant,n is take from array vx
%ex: vx=[10 11 12 13 14 15] => vy=[ 1 0 1 1 1 2]
%my code is
vy=[]
for i=1:length(vx)
str='';
j=1;
while length(str)<vx(i)
str=strcat(str,num2str(j));
j=j+1;
end
vy=[vy str2num(str(vx(i)))];
end
%the code is success with litte vx,but with lagre vx it over max loop of matlab,so how could i fix
Jonas on 16 May 2021
maybe it helps if you have a look into the width of numbers: the numbers from 0:9 have size ceil(log10(number))=1, after that the numbers from 10:99 have width ceil(log10(numbers))=2 and so on. this way you could have a look only on the numbers in the decade you are interested in.
by the way, how big gets your n? you can easily use smth like
sprintf('%i',1:10000)
and then extract the numbers you are interested in?