Problem 47. Extract leading non-zero digit

Created by Cody Team

Solve Later

{"relationships":[{"relationshipType":"http://schemas.mathworks.com/matlab/code/2013/relationships/document","targetMode":"","relationshipId":"rId1","target":"/matlab/document.xml"},{"relationshipType":"http://schemas.mathworks.com/matlab/code/2013/relationships/output","targetMode":"","relationshipId":"rId2","target":"/matlab/output.xml"}],"parts":[{"partUri":"/matlab/document.xml","relationship":[],"contentType":"application/vnd.mathworks.matlab.code.document+xml","content":"<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<w:document xmlns:w=\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\"><w:body><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:hyperlink w:docLocation=\"http://en.wikipedia.org/wiki/Benford%27s_law\"><w:r><w:t>Benford's Law</w:t></w:r></w:hyperlink><w:r><w:t> states that the distribution of leading digits is not random. This is probably because many things grow logarithmically. Extract the leading digit from these vectors.</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"ListParagraph\"/><w:numPr><w:numId w:val=\"1\"/></w:numPr></w:pPr><w:r><w:t>10 --&gt; 1</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"ListParagraph\"/><w:numPr><w:numId w:val=\"1\"/></w:numPr></w:pPr><w:r><w:t>13 --&gt; 1</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"ListParagraph\"/><w:numPr><w:numId w:val=\"1\"/></w:numPr></w:pPr><w:r><w:t>0.3 --&gt; 3</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"ListParagraph\"/><w:numPr><w:numId w:val=\"1\"/></w:numPr></w:pPr><w:r><w:t>-4 --&gt; 4</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"ListParagraph\"/><w:numPr><w:numId w:val=\"1\"/></w:numPr></w:pPr><w:r><w:t>-5 --&gt; 5</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"ListParagraph\"/><w:numPr><w:numId w:val=\"1\"/></w:numPr></w:pPr><w:r><w:t>-0.006 --&gt; 6</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>Input will be a vector</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"code\"/></w:pPr><w:r><w:t><![CDATA[ x = [1 0.3 -2 0.001 -0.0006, 582398, 3020];]]></w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>Output should be</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"code\"/></w:pPr><w:r><w:t><![CDATA[ y = [1 3 2 1 6 5 3];]]></w:t></w:r></w:p></w:body></w:document>"},{"partUri":"/matlab/output.xml","contentType":"text/xml","content":"<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\" ?><embeddedOutputs><metaData><evaluationState>manual</evaluationState><layoutState>code</layoutState><outputStatus>ready</outputStatus></metaData><outputArray type=\"array\"/><regionArray type=\"array\"/></embeddedOutputs>"}]}

Solve

Solution Stats

2869 Solutions
1167 Solvers

Last Solution submitted on Dec 01, 2020

Last 200 Solutions

Problem Comments

3 Comments

3 Comments

Ned Gulley on 29 May 2012

I added some extra test cases to fail some of the bogus answers.

Iván Quintanar on 31 Dec 2017

Amazing Law!!!!!!!!!!!!

Luyu Wang on 6 Jul 2018

I cannot understand the problem.

Solution Comments

Solution 793823

1 Comment

1 Comment

Fatpuss on 14 Dec 2015

Interesting. Looks like it failed due to some rounding issue.

Solution 701765

1 Comment

1 Comment

Swapnil Kulkarni on 16 Jul 2015

Whats wrong here ?

Solution 363899

1 Comment

1 Comment

Jon on 4 Dec 2013

This appears to be the best solution that doesn't use regexp

Solution 319044

1 Comment

1 Comment

Mineralter on 30 Sep 2013

A good method. num2str

Solution 113233

1 Comment

1 Comment

Konrad on 7 Dec 2012

Sorry, I did not want to copy you! Just tried to understand what you did...

Solution 30000

1 Comment

1 Comment

Aurelien Queffurust on 24 Feb 2012

Doesn't work if x = 0.3000

Solution 23182

1 Comment

1 Comment

Aurelien Queffurust on 24 Feb 2012

The best solution n codesize for me and w/o cheating !

Solution 14949

4 Comments

4 Comments

Show 1 older comment

Trung Duong on 8 Feb 2012

not fun at all :-)

Peter Wittenberg on 30 Mar 2012

bm, you have many good solutions in Cody. Why put in garbage like this?

Nigel Davies on 29 May 2012

You have just made me sad. Sorry.

@bmtran (Bryant Tran) on 30 May 2012

i wrote this a long time ago (on the third day of Cody). i figured that as soon as the test suite was changed, this solution would be gone with the wind. sorry to anyone i offended :(

Solution 11826

1 Comment

1 Comment

Aurelien Queffurust on 24 Feb 2012

Doesn't work if x = 0.3000

Solution 8808

1 Comment

1 Comment

the cyclist on 27 Jan 2012

Not general. Solution depends on the particular test case.

Solution 2421

1 Comment

1 Comment

Aurelien Queffurust on 24 Feb 2012

Doesn't work if x = 0.3000

Problem Recent Solvers1167

Problem Tags

math mathematics maths

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Problem 47. Extract leading non-zero digit

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers1167

Suggested Problems

More from this Author95

Problem Tags

Community Treasure Hunt

Problem 47. Extract leading non-zero digit

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers1167

Suggested Problems

More from this Author95

Problem Tags

Community Treasure Hunt

Players