mink and maxk functions

Question

UET Hussain 2018-2-5

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https://ww2.mathworks.cn/matlabcentral/answers/380779-mink-and-maxk-functions

评论： UET Hussain 2018-9-5

I'm using MATLAB R2017a. While trying to use "mink" and "maxk" functions, the MATLAB responds "Undefined function or variable 'maxk'." These two functions were introduced in R2017b. Is it possible to use these functions with R2017a? if yes, then how?

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Stephen23 2018-2-5

"These two functions were introduced in R2017b. Is it possible to use these functions with R2017a?"

No.

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Answer 1

Birdman 2018-2-5

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在 MATLAB Online 中打开

One approach would be writing your own function:

function y=mink(A,k)
A=sort(unique(A));
y=A(1:k);
end

Call this function from command line as follows

A=1:10;
mink(A,3)

and the first three smallest elements will be displayed.

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Jan 2018-2-5

在 MATLAB Online 中打开

mink does not reply unique elements. Therefore the correct replacement is:

function y = mink(A, k)
A = sort(A);   % No UNIQUE here
y = A(1:k);
end

See: mink([1,1,2,3], 2) replies [1,1,2] .

Birdman 2018-2-5

Mine approach was different, but anyway thanks Jan :)

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Answer 2

Salam Ismaeel 2018-9-4

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https://ww2.mathworks.cn/matlabcentral/answers/380779-mink-and-maxk-functions#answer_335458

编辑：Salam Ismaeel 2018-9-4

在 MATLAB Online 中打开

% function [B BIndex RestVector]= maxk2(A, k)
% Find k largest elements in a Vector A
% B : Vector with all max elements (included repeated) 
% BIndex : idx of max k element 
% RestVector : rest of the elements without max k elements 
function [B BIndex RestVector]= maxk2(A, k)
B = 0;
RestVector = A;
sumIndex = 1;
for i=1:k
  MaxA = max(A);
  I = A == MaxA;
  sumI = sum(I); %To find number of Max elements (repeated) 
  B(sumIndex: sumIndex+sumI-1) = MaxA; % to same max elements in B
  BIndex(sumIndex: sumIndex+sumI-1) = find(A == MaxA); 
  sumIndex = sumIndex + sumI; 
  A(I) = min(A); % exchange the max elements by a smallest value  
end
RestVector(BIndex) = [];  % remove largest values
------------------------------ Example ------------------
>> x
x =
     4    17    65    73    65    45    55    30    74    19
>> [x1 x1idx x1new ] = maxk2(x,4)
x1 =
    74    73    65    65    55
x1idx =
     9     4     3     5     7
x1new =
     4    17