storing a matrix as a collection in MongoDB

Question

I have a bunch of points {A, B, C, ...., X} and I want to store their distances in a matrix. One extra complication is that the distance from A to B and not the same as the distance from B to A, they are asymmetric.

My aim is to store this matrix in a collection in MongoDB but I really don't know how to, is that possible? any advice/ guidance is much appreciated.

you can provide a more complete example of the structure you want to save? These points are geographical coordinates? — Leonardo Delfino, Feb 05 '15 at 23:59
@LeonardoDelfino The points are geographical coordinates; latitude and longitudes. I want to store the distances between these points, for any two points the distance from point A to point B is not the same as the distance from point B to point A. Essentially I want to store a distance matrix in mongo and I want it to be able to give it any two points (lets say B and D) and then retrieve the distance between them. — MTA, Feb 06 '15 at 11:24

score 0 · Answer 1 · answered Feb 05 '15 at 23:56

0

MongoDB supports store Geospatial objects providing a particular way to create indexes and perform query these objects.

Take a look at :

http://docs.mongodb.org/manual/applications/geospatial-indexes/

and see if that is what you are looking for.

answered Feb 05 '15 at 23:56

Leonardo Delfino

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I don't know how 2Dsphere index will work.. Basically I have a table that stores all the places (with longitude and latitudes) but I want to calculate the distances using google maps API and insert them in a different collection in Mongo. – MTA Feb 06 '15 at 12:06

score 0 · Accepted Answer · answered Feb 06 '15 at 15:07

What measure of "distance" are you using, out of curiosity? Technically, you can't call a function d(X, Y) a "distance" unless d(X, Y) = d(Y, X) always. Distance between points on a sphere is symmetric so you can't be using that metric. If all you want to do is store and retrieve values d(X, Y), just store documents like

{
    "from" : X,
    "to" : Y,
    "distance" : 691
}

where X and Y are whatever kind of values are appropriate. Put an index on { "from" : 1, "to" : 1 } and then define

function d(X, Y) {
    return db.distances.findOne({ "from" : X, "to" : Y }).distance
}

storing a matrix as a collection in MongoDB

2 Answers2