Problem 44352. The Top 5 Primes

Created by Peng Liu

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This problem series invites you to solve two simple problems related to the integer NUMBER FIVE, in order to celebrate <a href = "https://www.mathworks.com/matlabcentral/cody/contests/1?s_tid=Cody5YA_cody_home">Cody's 5th birthday</a>.In this problem, let's find the top 5 greatest prime numbers along the first non-singleton dimension of an input array.Example<ul><li>If the input is a vector, the output is a length-5 vector containing the top 5 prime numbers of the input sorted in descending order. Append NaNs as needed in the output if the number of primes is less than 5.</li></ul><pre class="language-matlab">x = 1:10;
y = [7 5 3 2 NaN];
</pre><ul><li>If the input is a m-by-n (m &gt;= 5) matrix, the output is a 5-by-n matrix containing the column-wise top 5 prime numbers of the input matrix sorted in descending order. Whenever there are less than 5 primes found in a specific column of the input, simply append NaNs as needed in the same column of the output.</li></ul><pre class="language-matlab">% Input x is a matrix
x = [17 6 3
 13 8 17
 1 2 5
 5 3 7
 7 11 2
 31 7 6];
</pre><pre class="language-matlab">% Output y
y = [31 11 17
 17 7 7
 13 3 5
 7 2 3
 5 NaN 2];
</pre>Previous problem in this series: <a href = "https://www.mathworks.com/matlabcentral/cody/problems/44342-spot-the-first-occurrence-of-5">Spot the First Occurrence of 5</a>

This problem series invites you to solve two simple problems related to the integer NUMBER FIVE, in order to celebrate <https://www.mathworks.com/matlabcentral/cody/contests/1?s_tid=Cody5YA_cody_home Cody's 5th birthday>.

In this problem, let's find the top 5 greatest prime numbers along the first non-singleton dimension of an input array.

Example

* If the input is a vector, the output is a length-5 vector containing the top 5 prime numbers of the input sorted in descending order. Append NaNs as needed in the output if the number of primes is less than 5.

x = 1:10;
  y = [7 5 3 2 NaN];

* If the input is a m-by-n (m >= 5) matrix, the output is a 5-by-n matrix containing the column-wise top 5 prime numbers of the input matrix sorted in descending order. Whenever there are less than 5 primes found in a specific column of the input, simply append NaNs as needed in the same column of the output.

% Input x is a matrix
  x = [17     6     3
       13     8    17
        1     2     5
        5     3     7
        7    11     2
       31     7     6];

% Output y
  y = [31    11    17
       17     7     7
       13     3     5
        7     2     3
        5   NaN     2];

Previous problem in this series: <https://www.mathworks.com/matlabcentral/cody/problems/44342-spot-the-first-occurrence-of-5 Spot the First Occurrence of 5>

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Last Solution submitted on Jul 24, 2023

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Problem 44352. The Top 5 Primes

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