array operation for merging two arrays

data_1=[10;20;30;40];
data_2=[40;10];
data_3=[11;12];
for i=1:numel(data_2)
idx(i)=find(data_2(i)==data_1); 
end

I need to merge data_2 and data_3 w.r.t idx array as follows;

merged_data=[10;11;12;40];

idx ([4 1]) determines the row number of 40 and 10 (data_2) within merged_data. Other row of the merged_data belongs to data_3.

data_2 and data_1 arrays always share at least 2 numbers. I need to merge data_2 and data_3 as an automatic way, keeping the order of rows w.r.t idx.

[Azzi Abdelmalek]

Duplicate question here: http://www.mathworks.com/matlabcentral/answers/284994-adding-rows-to-array-with-order

[sermet]

Azzi, please read my comment in the previous question.

Answer 1

[Andrei Bobrov]

union(intersect(data_1,data_2),data_3)

or

merge_data = data_1
merge_data(~ismember(merge_data,data_2)) = data_3

[sermet]

Andrei, it doesn't work all the time. Assume,

data_2=[20;30];
idx=[2 3];

Then, merged_data should be;

merged_data=[11;20;30;12];

but merged_data from your code;

merged_data=[11;12;20;30]; % it is ascending mode thus the order cannot be protected.

20 should be in the second row of the merged_data and 30 should be in the 3rd row of the merged_data w.r.t. idx array.