Problem 2585. How to reverse spdiags?

Created by Jean-Marie Sainthillier
Appears in Are You Smarter Than a MathWorker?

Difficulty:Rate

Solve Later
Add To GroupÃ‚

The spdiags function extracts all nonzero diagonals from the m-by-n matrix A.
So if
  A = [1 2 3;4 5 6;7 8 9]
then
  spdiags(A) = [7 4 1 0 0;
                0 8 5 2 0;
                0 0 9 6 3]
But if I give you spdiags(A), can you give me A ?

Solve

Solution Stats

238 Solutions
39 Solvers

Last Solution submitted on May 04, 2025

Last 200 Solutions

Problem Comments

1 Comment

1 Comment

Paul Berglund on 5 Oct 2014

% this problem is not guaranteed solvable
isequal(spdiags([eye(5) zeros(5)]),spdiags(eye(5)))

Solution Comments

Show comments

Problem Recent Solvers39

Problem Tags

Community Treasure Hunt

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

Start Hunting!

Problem 2585. How to reverse spdiags?

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers39

Suggested Problems

More from this Author43

Problem Tags

Community Treasure Hunt

Problem 2585. How to reverse spdiags?

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers39

Suggested Problems

More from this Author43

Problem Tags

Community Treasure Hunt

Players