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Add contents of two columns to new columns with a delimiter between them

Asked by Rogier Busscher on 24 May 2017
Latest activity Commented on by dpb
on 26 May 2017
I have a matrix of 11693682x3 uint8. I would like to create so called 'keys' for my data in a new column. For example:
1, 2, 3
2, 5, 7
3, 3, 6,
4, 29, 0
Output:
1, 2, 3, 1|2
2, 5, 7, 2|5
3, 3, 6, 3|3
4, 29, 0, 4|29
Could anyone point me at the best way to solve this?

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2 Answers

Answer by dpb
on 24 May 2017

Well, it's simply impossible to add something like that as another column in an int8 array.
To do something similar you could create a corollary variable
>> key=categorical(cellstr(num2str(rb(:,1:2),'%d|%d')))
key =
1|2
2|5
3|3
4|29
>>
I'd suggest more conventional hashing techniques might be more useful, though. What's the end use here?

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I do not think i've made myself fully clear. I got a 11318560x3 matrix of all possible combination of Origin, Station and Destination.
Furthermore, i have travel time data on:
Any origin (A) to any station(B).
Any station(B) to any destination(C).
So i want to link the trips to that begin and end at the same station. That will result into a matrix of data where 'people' go from every origin to every destination, by using every station possible (A|B|C)
Then, I must find the lowest value for every origin-destination (A|C), so that i know what the lowest possible travel time is between each origin and destination.
So that is where i want to use the keys for, because it should be possible to find the lowest value in column K for each unique value (the keys) in Column J
But if you have a faster/better solution for this problem, i'm open to suggestions.
I thought you were looking for a way to find the given pair; the above does that by locating where that pair is in the vector.
If it's two sets, then just combination of
key1==val1 & key2==val2
is the same result.

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Answer by Walter Roberson
on 25 May 2017

If you only need to know what the distance is for each combination, but you do not need the path for each combination, then you can use https://www.mathworks.com/help/matlab/ref/graph.distances.html
If you need to know the path, then you can loop through all sources and use https://www.mathworks.com/help/matlab/ref/graph.shortestpath.html to all destinations.

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