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Jul
7
comment Dataset vs an association of associations
That's a useful way to convert between the two forms depending on the needs. Many thanks.
Jul
4
comment Dataset vs an association of associations
Wow - thanks for the detailed answer and context for Dataset. The general guideline is understood: Dataset[] for basic data types in record format and other constructions for more complicated expressions.
Jul
3
awarded  Nice Question
Jul
2
awarded  Commentator
Jul
2
revised Dataset vs an association of associations
deleted 4 characters in body
Jul
2
comment Dataset vs an association of associations
You're right. The question remains (it doesn't affect the purpose and the results of my entry) but I've improved the syntax of the assoc2lev definition. I think it's an interesting question and I'm hoping for some suggestions.
Jul
2
asked Dataset vs an association of associations
Jan
6
comment Unnecessary and slow conversion between simple polygons and geometric regions
Thanks Sjoerd - tried your suggestion (DiscretizeGraphics @ Graphics @ testpoly) to see what happens. Unfortunately working on all polygons at once is much slower by roughly a factor 20 with respect to Map[]. Looks like I'm stuck unless Wolfram Research can come up with a better solution.
Jan
5
comment Unnecessary and slow conversion between simple polygons and geometric regions
Thanks - just to clarify that I'm after the RegionUnion[] function on it's own. RegionCentroid[] and RegionMeasure[] were shown as examples of region functions which did not require the (slow) conversion from the graphics primitives to region objects.
Jan
5
asked Unnecessary and slow conversion between simple polygons and geometric regions
Dec
16
comment Simple image processing very slow
I think this only addresses two out of the three elements: reading the image and scaling the pixel values. It does not address the retrieval of the pixel positions.
Dec
16
revised Simple image processing very slow
I extended the timing experiment to use the SparseArray[] technique mentioned by Simon Woods and added extra processing to the results of the PixelValuePositions[] to ensure coordinates returned are in the same coordinate system as the other two techniques.
Dec
15
answered Simple image processing very slow
Oct
22
awarded  Yearling
Oct
8
comment Getting the coordinates of GeoDisk[] and similar Mathematica 10 GeoObjects
Brilliant - many thanks. I'm wondering for cases whether the first two geographic objects will always be those related to the background display ? If this is true the object extraction process can be automated and findcoordinates[] will only require one parameter.
Oct
7
awarded  Student
Oct
7
asked Getting the coordinates of GeoDisk[] and similar Mathematica 10 GeoObjects
Sep
24
awarded  Autobiographer
Aug
20
comment How to check if a 2D point is in a polygon?
Worth pointing out too that the "Canada" polygon example assumes implicitly that each vertex defining the polygon can be connected by a straight line. This has to be a good assumption for such a densely sampled contour. However, for large geographical polygons with few points the connecting edges should be modelled as "great circles".
Aug
16
comment How to check if a 2D point is in a polygon?
I don't think we will find a better solution in terms of performance unless perhaps a GPU-solution can be implemented (way above my programming skills in any case). One minor point - you're actually testing 10000 pairs of coordinates (points) not 20000.