Problem 796. Removing rows from a matrix is easy - but what about inserting rows?

Created by Dirk Engel

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619 Solutions
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Last Solution submitted on Feb 27, 2023

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3 Comments

Sean de Wolski on 27 Jun 2012

Many of the test cases are wrong.

For example:

A = (1:2:10)';
IND = 1:5;
b = (2:2:10)';
y_correct = (1:10)';

y_correct should be [2:2:10,1:2:10]'

The zeros one has zeros that are the wrong size etc.

Dirk Engel on 27 Jun 2012

I corrected one error regarding isequal with NaNs, but all the other test cases are correct.
A = [1 3 5 7 9]; IND = [1 2 3 4 5]; b = [2 4 6 8 10]; definitely should result in [1 2 3 4 5 6 7 8 9 10]! You have to insert b(1) after A(1), b(2) after A(2) and so on.

Christian Schröder on 9 Jul 2019

Nice problem, but the specification could be improved: from the description, you'd think the entire matrix b is supposed to be inserted after each row in IND; it's only the first example that makes it clear that this is not the case.

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Solution 1180413

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yurenchu on 5 May 2017

This works under the presumption that IND is already sorted (as is the case in the test suite).

Solution 193625

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1 Comment

yurenchu on 5 May 2017

Nice trick! But it breaks when IND contains 0s (inserting rows at the top of the matrix).

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Problem 796. Removing rows from a matrix is easy - but what about inserting rows?

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Problem 796. Removing rows from a matrix is easy - but what about inserting rows?

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