topic Re: Searching data points in a cluster in LabVIEW

Searching data points in a cluster

deepen_solanki — Sat, 23 Apr 2016 18:15:23 GMT

Hello.

I am using LabVIEW 2013 for myRIO. Im facing a problem with implementing a few things with clusters.

Problem Statement : Map co-ordinates logged from a GPS onto a map and use cursor functionality to check value of different sensors on different parts of the track.

I have been able to map the logged co-ordinates onto a map in LabVIEW. I create an array of the co-ordinates, bundle them and then feed it to an XY graph. Cursor has also been implemented. I click the map and drag my mouse and it takes me to various co-ordinates.

What I cannot do is display the other senors data for those co-ordinates of X,Y.

My plan is to bundle all the sensors data into a cluster and then try and search the cluster for needed points of X,Y.

How do I search within a cluster specifying only X,Y

eg: I give X,Y and i get the value of all sensors for that pair of X,Y ?

Thanks 🙂

Re: Searching data points in a cluster

Bob_Schor — Sat, 23 Apr 2016 18:27:47 GMT

We would understand much better what you are doing if you attach your code (the VI or a ZIP file with the entire Project). It would also be a good idea to give us some idea of the expected magnitude of the problem -- for example, if you are talking about 5-10 clusters, a brute-force "test every cluster" is certainly easy to program and probably within a factor of 2-3 of the best you could do.

Bob Schor

Re: Searching data points in a cluster

altenbach — Sat, 23 Apr 2016 18:39:03 GMT

XY graphs take a rich variety of data types so you have a choice to pick the best representation for the problem. (complex array, array of points, cluster of x and y arrays, etc)

I am assuming you currently have an array of xy clusters ("points") and not some fancy more complicated clusters. Is the data quantized to a grid or does it have near infinite resolution? Do you want the closest sensors (e.g. sorted by distance from the clicked coordinates) or only the exact locations?

Yes, please show us some simplified code with simulated data.

Re: Searching data points in a cluster

deepen_solanki — Sat, 23 Apr 2016 18:45:18 GMT

Okay, as of now what I am doing is creating two random arrays of X and Y co-ordinates to plot on the map and creating 2 more arrays of random numbers to represent sensor data. All this has been combined into a cluster. Now what I want to do is input X,Y and find the data value of the other sensors for that pair of X,Y. Basically I want the data of all sensors at that co-ordinate of the map.

Attached is a very rough VI I am working with

Re: Searching data points in a cluster

altenbach — Sat, 23 Apr 2016 18:54:07 GMT

Use the "cursor index" property and index into the array of point of the xy graph. (I would even use a complex 1D array instead)

Similarly, if the sensor data is also in an array withe the same number of points and arranged the same way, index into those to to get the seonr data.

Re: Searching data points in a cluster

altenbach — Sat, 23 Apr 2016 18:57:33 GMT

for example like this....

Re: Searching data points in a cluster

deepen_solanki — Sat, 23 Apr 2016 19:17:26 GMT

Why doesnt this work ?

Re: Searching data points in a cluster

deepen_solanki — Sat, 23 Apr 2016 19:54:05 GMT

Also, where is the part where I can search for sensor data giving X,Y as inputs ?

Re: Searching data points in a cluster

altenbach — Sat, 23 Apr 2016 21:15:14 GMT

Sorry, posting by phone. Cannot see your VI. Make sure the cursor is locked to a plot (obviously does not work with free cursors). As I said, if your sensor data is arranged as your points, there is no need for "searching".

Re: Searching data points in a cluster

altenbach — Sun, 24 Apr 2016 06:33:25 GMT

@deepen_solanki wrote:
Why doesnt this work ?

OK, looking at you code...

I don't expect it to work, because none of it makes much sense.

Try something along my earlier suggestion. Here's a very rough draft.

Re: Searching data points in a cluster

deepen_solanki — Sun, 24 Apr 2016 10:00:22 GMT

@altenbach

I am attaching the code I wrote, but I must say, your code is beautiful. It is exactly what I wanted.
Can you briefly explain how this works ?

Thank you ! 🙂

Re: Searching data points in a cluster

altenbach — Sun, 24 Apr 2016 15:43:11 GMT

Your code has several problems, for example equal comparisons on DBL are always problematic once you have real data. If X and Y are always integers, you should use a blue datatype.

Looking at your new code (Please give the VI a new name when attaching new and different code!!!): SInce there is an absolute upper limit on the number of iterations, you need a FOR loop, not a while loop. You can show the conditional terminal to stop early if needed. I would also rewrite the boolean logic. It would be much easier to understand using "stop when true", removing the "NOT", and adjusting the other comparisons.

There is also "search array", which would work perfectly using complex data. (See attached draft).

Now to my code: data for an xy graph is an ordered set of points (irrenspective of the exact representation (complex array, array of ponts, clust of x and y arrays, etc.) and if a cursor is locked to a plot (as in your case), only valid points can be selected. The current cursor has an x and a y, but also an index (Cursor.Index) that tells you which one of the data points is current.ly under the cursor. You can also get the same data out of a cursor move event data node (Point.Idx). (It is somewhat unfortunate that the same function is named differently between events and property nodes, but that's how it is...)

Note that I rearranged the data as array of scalar clusters (instead your cluster of arrays), by using a FOR loop, It is more suitable for the problem. You get all values using a single index whereas in your arrangement it is more difficult to access the values.