On Monday, August 25, 2014 4:46:11 AM UTC-4, Rémi Cura wrote: > > You want to map your dimension > (time, note_pitch) to (X,Y) ? > > It seems really difficult to achieve if for instance you would consider a > C and a C up an octave closer than a C and a D. > > And if you consider > (time,note_pitch) to (X=time, Y = [A-G], Z = [1-8]) , > Lot's of function in postgis doesn't work well with Z. >
Fortunately we can map musical notes as 1-12 instead of A - G, or for that matter 1-88. As "vectors" the notes can range from -88 to 88 (keys on the piano), bounded somewhat by abs( vector1+vector2+vector3 ) <= 88. In other words instead of an X,Y coordinate system, a musical note is 1 dimension (y), time the 2nd dimension (x). Analyzed as a directed path (geometrically left to right .. ) the query would be analyzing time instead of a physical "x" coordinate (i.e. longitude). So if "X" is time & "Y" is pitch, can I quantize time by arbitrarily discrete amounts & still get usable results? Say for example we establish the 1/32nd note as being the smallest duration, then everything would be an integer multiple of that. It's surely not a perfect model, but a cartesian reduction of a certain problem for quick analyses. An example of what I'm thinking: Using multilines, it could be possible to observe where a melody & it's counterpoint harmony cross over. Or draw a chord as a polygon & see where a melodic line crosses through it. I wondering what other types of metrics I can derive from a cartesian geometry? For instance, I gather PostGIS can find polylines ranked by similarity? If so this could be superior to my trigram dictionary attack method, or bothering with an FP-Growth algorithm. > Moreover, distance between geometry (serei of not ein your case) in postgis are rather limited to > _what you can come up with > _*ST_HausdorffDistance*() > (you could use R to create your own distances) TY for the pointer. I'm very much considering using R as a stored procedure language to work over these data. > I'm not an expert but lots of work in GIS rearch is devoted to time serie, mainly GPS trace (X,Y,Z,timestamp). > It seems that Grass GIS has a module for it : http://grasswiki.osgeo.org/wiki/Time_series Yeh, that's the USACE GIS db. Another thing to look into... :) Thanks! --Lee
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