Inserting zeros for missing values in a vector

Question

Dom 2023-4-3

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1940529-inserting-zeros-for-missing-values-in-a-vector

评论： Jon 2023-4-6

采纳的回答： Jon

% ID is an index

% IDx is a 'result' (Values in Vx conform to IDx)

% Index values 1 and 4 and missing in IDx (when compared with ID)

% I want to put a zero in Vx at positions 1 and 4

% This code works - newVx has zeros in right places

ID=[1:5]';

IDx=[2,3,5]';

Vx=[10,15,20]';

newVx=NaN( size( ID ) );

newVx (ismember(ID,IDx)) = Vx;

newVx = fillmissing(newVx,'constant',0)

%

% but if the problem is repeated (below)

% I get an error message:

% Unable to perform assignment because the left and right sides have a different number of elements.

%

ID=[1:5]';

ID2=repmat(ID,2,1);

IDx=[2,3,5,1, 4]';

Vx=[10,15,20, 30, 40]';

newVx=NaN( size( ID2 ) );

newVx (ismember(ID2,IDx)) = Vx;

newVx = fillmissing(newVx,'constant',0)

%

% In this case newVx should look like this:

% ID newVx

% 1 0

% 2 10

% 3 15

% 4 0

% 5 20

% 1 30

% 2 0

% 3 0

% 4 40

% 5 0

%

% Appreciate suggestions for a solution - my ID vector is of length 97 and is repeated 15 times(1455 x 1)

% Length of (IDx &) Vx is 1208

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Jon 2023-4-4

在 MATLAB Online 中打开

You could do this:

% define number of products
numProducts = 5;
% Define products and there export values
products = [2,3,5,1,4]
value = [10,15,20,30,40];
% Assume that when product list goes to a lower value we are on to the next
% country, then assign corresponding row index in full matrix 
country = cumsum([1 diff(products)<0])% gives country number
rowIdx = (country-1)*numProducts + products;
% Make output data array with first column product id's second column
% export value
numCountries = max(country);
exportValues = zeros(numCountries*numProducts,2);
expValues(:,1) = repmat((1:numProducts)',2,1); % product id's
expValues(rowIdx,2) = value

Jon 2023-4-4

Please note the above solution will not work if you have some countries that do not export anything, as there will be no way to detect that there is a missing country in your products vector. If you have to cover this edge case then further development will be required

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Answer 1

Jon 2023-4-3

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1940529-inserting-zeros-for-missing-values-in-a-vector#answer_1207799

At line 22 on the right hand side you have the vector Vx which has 5 elements. On the left hand side you have newVx indexed by ismember(ID2,IDx). Evaluating ismember(ID2,IDx) you see that it is true for all 10 elements of ID2. So you are trying to assign a 5 element vector to a 10 element vector and MATLAB can't do that, thus the error.

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Dom 2023-4-4

Thank you Jon, for spending time thinking about this issue.

Just a few points. The first example works. The second does not. In both cases there is a difference in the number of elements.

Case 1: dim(ID)>dim(IDx) Case 2: dim(ID2)>dim(IDx). So the issue I think as you have identifed in your comment is: The elements of ID are unique, but the elements of ID2 are not since they repeat themselves. So I suspect that is where the problem is.

Let me try and explain again what I am trying to do. Suppose I have 5 products and 2 countries.

Products are indexed 1 through 5. - so ID repeats twice (ID2).

Then I have two vectors or a matrix with two columns: Col 1 (or vector 1) - contains an index of the product that country 1 exports. It typically does not export all 5 products. In my second example Country 1 exports products 2, 3 and 5 and Country 2 exports products 1 and 4 (IDx=[2,3,5,1, 4]';). Vx (or column 2 of a matrix) is the value of exports for the products exported by countries 1 and 2. (so dim(IDx)=dim(Vx)).

I want newVx to look like what I wrote out above. The new Vx has zero values for products that each country does not export. And dim(ID)=dim(newVx).

Thank you again,

Dom

Dom 2023-4-5

Thanks Jon, That works. Appreciate your effort.

Jon 2023-4-6

Your welcome, interesting problem. If this solved your problem could you please accept the answer. This way if someone else has a similar issue they will know that a solution is available.

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