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Counting the number of digits

Asked by joseph Frank on 3 Jul 2011

Hi,

how can I compute the number of digits A=[12875] how can I get 5 as the number of digits in A?

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joseph Frank

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5 Answers

Answer by bym on 3 Jul 2011
Accepted answer

One way:

numel(num2str(A))

3 Comments

Paulo Silva on 3 Jul 2011

I made the stupid mistake of using -'0' when it wasn't needed so I'm voting on your answer and removing mine.

Oleg Komarov on 3 Jul 2011

Fails with decimals. Ex: n = 99.3;

Walter Roberson on 15 Jul 2011

Fails with negative numbers too.

bym
Answer by Oleg Komarov on 3 Jul 2011

To count integer part

ceil(log10(abs(A)))

Edit

floor(log10(abs(A)+1)) + 1

3 Comments

Walter Roberson on 15 Jul 2011

Fails on [-1,1] and all exact powers of 10.

Jan Simon on 15 Jul 2011

ceil(log10(abs(A) + 1)) ?

Walter Roberson on 15 Jul 2011

Fails on 0, Jan.

Over integral values:

ceil(log10(max(1,abs(A)+1)))

Over real numbers,

ceil(log10(max(1,abs(A)*(1+eps))))

I think.

Oleg Komarov
Answer by Jaymin on 13 Dec 2012

Long, but it gets the job done.

numel(num2str(A))-numel(strfind(num2str(A),'-'))-numel(strfind(num2str(A),'.'))

0 Comments

Jaymin
Answer by Stephanie on 26 May 2013
numel(num2str(fix(abs(A))))

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Stephanie
Answer by Turner on 16 Aug 2013
Edited by Turner on 19 Aug 2013

Will do the trick for all nonzero integers:

fix(abs(log10(abs(A))))+1

For a 10,000 iteration benchmark with some above answers:

Jaymin= 1.423717 seconds; Stephanie= 0.476135 seconds; Mine= 0.000878 seconds

If you don't expect 0s to appear, this is the fastest and most accurate method. Only works for decimals that satisfy -1<A<1.

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Turner

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