Problem 972. Set a diagonal

Created by Nicholas Howe
Appears in Indexing II

Difficulty:Rate

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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.
For example,
M = magic(5);
setDiagonal(M,1:4,-1)
ans =
  17    24     1     8    15
   1     5     7    14    16
   4     2    13    20    22
  10    12     3    21     3
  11    18    25     4     9

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Last Solution submitted on Oct 26, 2025

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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

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

Anton Casas on 2 Nov 2020

Test cases with 2 input arguments can be very tricky for people without knowledge of nargin, and that is off-topic here. I think a hint should be added on the problem description.

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Problem 972. Set a diagonal

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Problem 972. Set a diagonal

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