Rename the indices of a vector in a certain way.

Question

LH 2024-7-4，13:46

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2134501-rename-the-indices-of-a-vector-in-a-certain-way

评论： Stephen23 2024-7-4，17:54

Hi all,

My code below has a vector A and its index vector idx. It goes throguh the elements of A and when it finds a zero element, it removes its index from the orginal index vector.

My problem here is: suppose the updated index vector is

. How can I rename this vector so it increases in an acending order? For example: the first element in the updated index vector is 1, I want this to be 1, the second element in the updated index vector is 3, I want this to become 2, and so on so forth.

%define the index vector
idx = [1 2 3 4 5];
%define the vector
A   = [5 0 6 0 3];
%initialise the vector that has all indices of zero elements
zero_indices = [];
%go through the elements of vector A
for uu = 1:numel(A)   
    %if the element is zero
    if A(uu)==0
        %assign its index to the zero-elements index vector
        zeroindex = uu;
        %collect all results from iterations
        zero_indices = [zero_indices ; zeroindex];
    end
end
%update the original index vector by removing the indicies that correspond
%to zero elements
idx(zero_indices) = [];
%rename the indices os that they beocome 1, 2, 3, ...

Any help would be appreicted.

Thanks.

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Answer 1

Garmit Pant 2024-7-4，14:30

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2134501-rename-the-indices-of-a-vector-in-a-certain-way#answer_1481266

在 MATLAB Online 中打开

Hello LH

Given that you have extracted the indices of non-zero elements in the vector ‘A’, you can rename the index vector to have ascending values using the following code-snippet:

% Given non-zero value indices are [1 3 5] 
idx = [1 3 5]; 
% Rename the indices so that they become 1, 2, 3, ... 
new_idx = 1:numel(idx); 
% Display the updated index vector 
disp('Updated index vector:'); 
Updated index vector:
disp(new_idx); 
     1     2     3

I hope you find the above explanation and suggestions useful!

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LH 2024-7-4，17:17

That's great! Many thanks Garmit!

Stephen23 2024-7-4，17:54

在 MATLAB Online 中打开

The simpler MATLAB approaches:

idx = [1,3,3,5,1,5,3,1]
idx = 1x8
     1     3     3     5     1     5     3     1
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<mw-icon class=""></mw-icon>
[~,~,idy] = unique(idx)
idy = 8x1
     1
     2
     2
     3
     1
     3
     2
     1
<mw-icon class=""></mw-icon>
<mw-icon class=""></mw-icon>
idy = discretize(idx,[unique(idx),Inf])
idy = 1x8
     1     2     2     3     1     3     2     1
<mw-icon class=""></mw-icon>
<mw-icon class=""></mw-icon>