I have two questions;
What is the name of the graph (or circuit) which goes along the outer vertices of existing nodes.
What will be the formal definition of that graph.
for the simplicity, I have added a sample figure and the red highlighted graph is what I wanted.
If I show how I got this outer vertices;
I have set of sub graphs. So I got UNION and INTERSECTION, then got the DIFFERENCE. Do this one after the other, Finally I ended with a graph which is similar to MY RED EDGE GRAPH.
So the final graph which I got was {1,2,6,7,9,8,10,11,10,7,6,5,3,4,3,1} if i start from 1.
PLEASE TELL ME WHETHER I AM USING CORRECT THING OR NOT AS I AM COMING TO END OF MY WORK.
You may be trying to define some kind of geometric hull, but surely not a graph property. These two graphs are equivalent and indistinguishable a far as Graph Theory goes:
Edit
Perhaps this old answer of mine may help you
Related
Here is what I want to do:
keep a reference curve unchanged (only shift and stretch a query curve)
constrain how many elements are duplicated
keep both start and end open
I tried:
dtw(ref_curve,query_curve,step_pattern=asymmetric,open_end=True,open_begin=True)
but I cannot constrain how the query curve is stretched
dtw(ref_curve,query_curve,step_pattern=mvmStepPattern(10))
it didn’t do anything to the curves!
dtw(ref_curve,query_curve,step_pattern=rabinerJuangStepPattern(4, "c"),open_end=True, open_begin=True)
I liked this one the most but in some cases it shifts the query curve more than needed...
I read the paper (https://www.jstatsoft.org/article/view/v031i07) and the API but still don't quite understand how to achieve what I want. Any other options to constrain number of elements that are duplicated? I would appreciate your help!
to clarify: we are talking about functions provided by the DTW suite packages at dynamictimewarping.github.io. The question is in fact language-independent (and may be more suited to the Cross-validated Stack Exchange).
The pattern rabinerJuangStepPattern(4, "c") you have found does in fact satisfy your requirements:
it's asymmetric, and each step advances the reference by exactly one step
it's slope-limited between 1/2 and 2
it's type "c", so can be normalized in a way that allows open-begin and open-end
If you haven't already, check out dtw.rabinerJuangStepPattern(4, "c").plot().
It goes without saying that in all cases you are getting is the optimal alignment, i.e. the one with the least accumulated distance among all allowed paths.
As an alternative, you may consider the simpler asymmetric recursion -- as your first attempt above -- constrained with a global warping window: see dtw.window and the window_type argument. This provides constraints of a different shape (and flexible size), which might suit your specific case.
PS: edited to add that the asymmetricP2 recursion is also similar to RJ-4c, but with a more constrained slope.
I would like to plot the direction field for a system of 3 or more equations in SageMath using Maxima. I know how to do this for a system of 2 equations. I don't know what to modify so that I extend it to 3 or more equations. I tried the following example for a system of two equations
maxima('plotdf([x,-y],[x,y],[x,-2,2],[y,-2,2])')
I was thinking for the three or more equations I simply have to add more varibles like
maxima('plotdf([x,-y,z],[x,y,z],[x,-2,2],[y,-2,2],[z,-2,2])')
but its not working. I dont know what am missing.
The Maxima documentation for plotdf makes the syntax clear. I'm not sure what a slope/direction field would look like for more equations unless you had more variables, but then it would have to be in three dimensions, which is not supported.
In any case I'm surprised this worked from within Sage; you must have had wxmaxima or something analogous already there.
Finally, note that SageMath has slope fields natively, though this may not correspond with your workflow.
I'm rather new to oracle spatial. I'd like to restrict shapes to simple polygons. multiple polygons are ok. donuts are not. crossed edges are not. and all shapes must be separated by a tolerance.
SDO_GEOM.VALIDATE_GEOMETRY_WITH_CONTEXT seems like a good place to start... but would appreciate any further insight on how to determine that I do not have donuts.
any insight appreciated.
found what I needed here:
https://spatialdbadvisor.com/oracle_spatial_tips_tricks/89/sdo_utilgetnumrings-an-alternative
with additional information from the documentation:
https://docs.oracle.com/cd/B28359_01/appdev.111/b28400/sdo_objrelschema.htm#SPATL020
I'm trying to run the hlda algorytmm and producing a descriptive hierarchy of the input documents. The problem is I'm running diverse parameters configs and trying to understand how it works in an "empirical way", because I can not match the ones that are being used in the original papers (I understand it's a different team). E.g. alpha in Mallet seems to be eta in the paper, but I'm not very sure. Besides, I can not know the boundaries for each of them. I mean, the range of possible values for each parameter.
In the source code, there is some help:
double alpha; // smoothing on topic distributions
double gamma; // "imaginary" customers at the next
double eta; // smoothing on word distributions.
First, I used the default values: alpha=10.0; gamma=1.0; eta = 0.1;
Then, I tryed running the algorythm by changing the values and interpret the results, but I can't understand the meaning of them. E.g. I think changing gamma (in Mallet) has an effect on the customers decition: to start a new node in the tree or to be placed in an existing one. So, if I set gamma = 0.5, less nodes should be produced, because 0.5 is half the probability of the default one, right? But the results with gamma=1 give me 87 nodes, and with gamma=0.5, it returns 98! And then, I'm asking me something new: is that a probability? I was trying to find the range of possible values in these two papers, but I didn't find them:
Hierarchical Topic Models andthe Nested Chinese Restaurant Process
The Nested Chinese Restaurant Process and BayesianNonparametric Inference of Topic Hierarchies
I know I could be missing something, because I don't have the a good background on this, but that's why I'm asking here, maybe someone already had this problem and can help me understanding those limits.
Thanks in advance!
It may be helpful to run multiple times with each hyperparameter setting. I suspect that gamma does not have a big influence on the final number of topics, and that what you are seeing could just be typical variability in the sampling process.
In my experience the parameter that has by far the strongest influence on the number of topics is actually eta, the topic-word smoothing.
We have an application that has a database full of polygons (currently stored as points) that a .net app pulls out and checks if they overlap.
I occurred to me that it would be much nicer to convert these point arrays to polygon / polyline objects within the database and use sql to get a bool of weather they overlap or not.
I have seen different methods suggested to do this but non of the examples given were quite in-line with my needs.
I would be very happy to receive input from those kind enough to offer their experience.
Additional:
In response to questions: It is indeed 2D. and yes any crossover of the two is considered true. The polygons have n points and can be concave. The polygons will be saved as 1 per row (after data conversion task) as polygons (i.e. the polygon type .. it might be called something else spatial / geom my memory is not on my side right now)
You can use .STIntersection with .STAsText() to test for overlapping polygons. (I really hate the terminology Microsoft has used (or whoever set the standard terms). "Touching," in my mind, should be a test for whether or not two geometry/geography shapes overlap at all, not just share a border.)
Anyway....
If #RadiusGeom is a geometry representing a radius from a point, the following will return a list of any two polygons where an intersection (a geometry that represents the area where two geometries overlap) is not empty.
SELECT CT.ID AS CTID, CT.[Geom] AS CensusTractGeom
FROM CensusTracts CT
WHERE CT.[Geom].STIntersection(#RadiusGeom).STAsText() <> 'GEOMETRYCOLLECTION EMPTY'
If your geometry field is spatially indexed, this runs pretty quickly. I ran this on 66,000 US CT records in about 3 seconds. There may be a better way, but since no one else had an answer, this was my attempt at an answer for you. Hope it helps!
Calculate and store the bounding rectangle of each polygon in a set of new fields within the row which is associated with that polygon. (I assume you have one; if not, create one.) When your dotnet app has a polygon and is looking for overlapping polygons, it can fetch from the database only those polygons whose bounding rectangles overlap, using a relatively simple SQL SELECT statement. Those polygons should be relatively few, so this will be efficient. Then, your dotnet app can perform the finer polygon overlap calculations in order to determine which ones of those really overlap.
Okay, I got another idea, so I am posting it as a different answer. I think my previous answer with the bounding polygons probably has some merit on its own, even if it was to reduce the number of polygons fetched from the database by a small percentage, but this one is probably better.
MSSQL supports integration with the CLR since version 2005. This means that you can define your own data type in an assembly, register the assembly with MSSQL, and from that moment on MSSQL will be accepting your user-defined data type as a valid type for a column, and it will be invoking your assembly to perform operations with your user-defined data type.
An example article for this technique on the CodeProject: Creating User-Defined Data Types in SQL Server 2005
I have never used this mechanism, so I do not know details about it, but I presume that you should be able to either define a new operation on your data type, or perhaps overload some existing operation like "less-than", so that you can check if one polygon intersects another. This is likely to speed things up a lot.