Array, grouping elements, adding their corresponding values and sorting from left to right

Question

Tadas Grauzinis 2019-11-21

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https://ww2.mathworks.cn/matlabcentral/answers/492464-array-grouping-elements-adding-their-corresponding-values-and-sorting-from-left-to-right

编辑： Tadas Grauzinis 2020-4-13

采纳的回答： David Hill

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Greetings

Im struggling with this problem. So I have an array :

X_Y=[4 7 6 9 7 10; 0.08 0.02 0.24 0.06 0.48 0.12]

and I need to group same value elements from first row and add their correspondig values from the second row. In this situation since there are two 7( 0.02+0.48). And lastly I need to sort the elements of first row in ascending order while maintaining their values from the second row.

The final array should look like this

X_Y=[4 6 7 9 10; 0.08 0.24 0.5 0.06 0.12]

How can I do this?

Thank you.

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Answer 1

David Hill 2019-11-21

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https://ww2.mathworks.cn/matlabcentral/answers/492464-array-grouping-elements-adding-their-corresponding-values-and-sorting-from-left-to-right#answer_402695

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My code is a little convoluted. There is likely a better way but it works.

a=[4 7 6 9 7 6 10 6; 0.08 0.02 0.24 0.06 0.31 0.48 0.12 0.45];
[b,x]=unique(a(1,:));
y=histc(a(1,:),b)<2;
c=a(:,sort(x(y)));
d=a(1,x(~y));
for k=1:length(d)
    c=horzcat(c,[d(k);sum(a(2,a(1,:)==d(k)))]);
end
[~,y]=sort(c(1,:));
c=c(:,y);

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David Hill 2019-11-22

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a=[4 7 6 9 7 6 10 6; 0.08 0.02 0.24 0.06 0.31 0.48 0.12 0.45];
[b,x]=unique(a(1,:));%b=[4,6,7,9,10] x=[1;3;2;4;7] the position of the first occurance
y=histc(a(1,:),b)<2;%this places 'a' into the b-bins and logically reports which bins contain only 1 count (y=[1 0 0 1 1])
c=a(:,sort(x(y)));%establish array c=[4,9,10;0.08,0.06,0.12] with no duplicates
d=a(1,x(~y));%finds values of a that have duplicates, d=[6,7]
for k=1:length(d)%cycles through the duplicates
    c=horzcat(c,[d(k);sum(a(2,a(1,:)==d(k)))]);%sums row 2 of a for the duplicates and concats to the end of matrix c
end
[~,y]=sort(c(1,:));%sorts the first row of c to get indexes of the sort
c=c(:,y);%finally, sorts both rows of c based on the sort-indexes to obtain what you wanted.