Problem 972. Set a diagonal

Created by Nicholas Howe

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:r><w:t>Given a matrix M, row vector v of appropriate length, and diagonal index d (where 0 indicates the main diagonal and off-diagonals are identified by positive and negative integers), return a new matrix where the specified diagonal of M is replaced by v. You may assume that v is the correct length for the specified diagonal. If d is not provided, assume it is zero.</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>For example,</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"code\"/></w:pPr><w:r><w:t><![CDATA[M = magic(5);\nsetDiagonal(M,1:4,-1)\n\nans =\n  17    24     1     8    15\n   1     5     7    14    16\n   4     2    13    20    22\n  10    12     3    21     3\n  11    18    25     4     9]]></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

585 Solutions
128 Solvers

Last Solution submitted on Oct 29, 2020

Last 200 Solutions

Problem Comments

9 Comments

9 Comments

Show 6 older comments

Nicholas Howe on 9 Oct 2012

Added new test case 9 Oct. 2012

Ned Gulley on 10 Oct 2012

Are you missing some text from your example?

Ned Gulley on 10 Oct 2012

Test suggestion: Stick a zero in one of your v vectors and you'll eliminate some of the shorter answers.

Jean-Marie Sainthillier on 11 Oct 2012

Yes. All solutions with find don't work with 0 in v.

Nicholas Howe on 14 Jan 2013

Thanks for the suggestions -- I updated the text, added a new test case and rescored.

yurenchu on 15 Apr 2017

@Nicholas Howe: The test suggestion meant: stick a 0 in v, and this 0 is meant to replace an entry of M that was unequal to 0. In other words: the new test-case doesn't make a difference (and hence is useless) if M is a null-matrix.

Ahsan Naeem on 10 Jun 2017

The cases with d=0 are working for me but your test cases are giving error..... What's this?

Riccardo Dessì on 25 Jun 2018

please, when you make use of test cases with floating point numbers specify a common precision, otherwise is impossible to pass the suite and people need to be noob! thx in advanced

Akrem Hadji on 17 Oct 2020 at 16:42

Please add a precision threshold for floating numbers. Sometimes I get results with an error ~ e-17 close, but still not accepted.

Solution Comments

Solution 1163886

1 Comment

1 Comment

yurenchu on 15 Apr 2017

Why does it fail Test #2?

Solution 1057893

1 Comment

1 Comment

yurenchu on 15 Apr 2017

Wouldn't work if d was undefined and M wasn't a diagonal matrix.

Solution 145079

2 Comments

2 Comments

Jean-Marie Sainthillier on 11 Oct 2012

I like the try/catch with ans

Khaled Hamed on 12 Oct 2012

It seems Matlab allows for many useful tricks. I was surprised at the behavior of 'diag' in the leading solution.

Problem Recent Solvers128

Problem Tags

diagonals indexing

Community Treasure Hunt

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

Start Hunting!

Problem 972. Set a diagonal

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers128

Suggested Problems

More from this Author11

Problem Tags

Community Treasure Hunt

Problem 972. Set a diagonal

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers128

Suggested Problems

More from this Author11

Problem Tags

Community Treasure Hunt

Players