table A:
lat | long | the_geom | code | sign
13.8433095 | 100.6360357 | 0101000020E61.... | ABC | start_point
13.7544738 | 100.5459646 | 0101000020E6..... | ABC | end_point
13.4124215 | 100.6232332 | 0101000020E61.... | DEF | start_point
13.2423438 | 100.2324426 | 0101000020E6..... | DEF | end_point
table B:
lat | long | the_geom | code
13.7546285 | 100.5458729 | 0101000020E.... | ABC
13.7546698 | 100.5458513 | 0101000020E.... | ABC
13.7547107 | 100.5458233 | 0101000020E.... | DEF
...
I would like to find the nearest point of each point (start and end pojnt) compare with every points with the same code in table B ?
What's the best PostGIS function/PostgreSQL query to solve this ?
If you are using recent versions of the software, you can quickly find the K nearest neighbors to a point in PostGIS using KNN-GiST techniques. Small values of K are fastest, and 1 is about as small as they get, so this should work very well for you. I've only used KNN-GiST with text trigrams, but I know they work with PostGIS, too -- I just don't know the best page to read to get started with it. A web search for "postgis knn gist" shows lots of likely candidates.
After a long time question, i just found the solution of "Nearest Neighbor"
http://www.bostongis.com/PrinterFriendly.aspx?content_name=postgis_nearest_neighbor_generic
Related
I need help with a project. Right now, I have a giant postgreSQL database (~6 million rows, 25 columns) and I need to figure out how to get the following information:
For one specific range for one attribute, "20<np<400":
Find local minimum values in another variable, "itt"
Record whole row of data for that local minimum
Add extra column and add to this the next local maximum of itt
Edit: the attribute are as follows: The database has this schema: id | at | itt | engine_torque | ng | np | fuel_flow | engine_oil_pressure | engine_oil_temp | airspeed | altitude | total_air_temp | weight_on_wheels | p25_p3 | bypass | chip_counter | number_of_flight_counter | number_of_engine_run | run_id | ectm_file_id | aircraft_sn | engine_sn | gas_generator_sn | power_section_sn | tail_number
By 'local minima and maxima' i mean that within a certain range of np, i'm looking for the highest and lowest values of itt in close proximity with respect to time, or "at"
Thanks in advance!!!
I have a table, Regions:
| id | name |
|----|----------|
| 1 | Jersey |
| 2 | Scotland |
...
and a table of RegionPoints (which define the bounding box for each region):
| id | regionid | lat | lng |
|----|----------|-------|-------|
| 1 | 1 | 49.27 | -2.27 |
| 2 | 1 | 49.27 | -1.99 |
| 3 | 1 | 49.15 | -2.27 |
| 4 | 1 | 49.15 | -1.99 |
...
Given a latitude and longitude, I want to find the regions which contain the given point.
From my understanding, I need to aggregate by regionid, then
use ST_ConcaveHull, followed by ST_Contains using the latitude and longitude to query for, however my concern is that with a large number of regions, computing a concave hull for each will be very inefficient.
This is my first time using PostGIS, so a bit stuck.
Yes, computing the concave hull "on the fly" can be inefficient with lots of data.
Also, you won't be able to use a spatial index, as your geometries are built at query time.
Using ST_MakeEnvelope instead of ST_ConcaveHull will mitigate the problem.
However, as JGH suggests, you should store those coordinates as polygons in the Regions table, using ST_MakeEnvelope to create them.
Than build a spatial index and use ST_Contains to get the regions that contains a point.
I want a Cross tab that lists field values and counts them instead of just giving a count for the summation. I know I could make this with groups but I cant list the values vertically that way. From my research I believe I have to use a Display String Formula.
SQL Field Data
-------------------------------------------------
| Play # | Formation |Back Set | R/P | PLAY |
-------------------------------------------------
| 1 | TREY | FG | R | TRUCK |
-------------------------------------------------
| 2 | T | FG | R | RHINO |
-------------------------------------------------
| 3 | D | FG | P | 5 STEP |
-------------------------------------------------
| 4 | D | FG | P | 5 STEP |
-------------------------------------------------
| 5 | K JET | NG | R | DOG |
-------------------------------------------------
Desired report structure:
-----------------------------------------------------------
| Backet & Formation | Run | Pass |
-----------------------------------------------------------
| NG K JET | BULLA 1 | |
| | HELL 3 | |
-----------------------------------------------------------
| FG D | | 5 STEP 2 |
-----------------------------------------------------------
| NG K JET | DOG | |
-----------------------------------------------------------
| FG T | RHINO | |
-----------------------------------------------------------
Don't see why a Crosstab is necessary for this - especially if the entire body of the report is just that table.
Group your records by Bracket and Formation - If that's not
something natively configured in your table, make a new Formula field
and group on that.
Drop the 3 relevant fields into whichever section you need to display. (It might be a Footer, based on whether or not you want repeats
Write a formula to determine whether or not Run or Pass are displayed, and place it in their suppression field. (Good luck getting a Crosstab to do that for you! It tends to prefer 0s over blanks.)
If there's more to the report than just this table, you can cheat the system by placing your "table" into a subreport. And of course you can stretch Line objects across the sections and it will stretch to form the table outlines
I know dataframes are supposed to be immutable and everything and I know it's not a great idea to try to change them. However, the file I'm receiving has a useless header of 4 columns (the whole file has 50+ columns). So, what I"m trying to do is just get rid of the very top row because it throws everything off.
I've tried a number of different solutions (mostly found on here) like using .filter() and map replacements, but haven't gotten anything to work.
Here's an example of how the data looks:
H | 300 | 23098234 | N
D | 399 | 54598755 | Y | 09983 | 09823 | 02983 | ... | 0987098
D | 654 | 65465465 | Y | 09983 | 09823 | 02983 | ... | 0987098
D | 198 | 02982093 | Y | 09983 | 09823 | 02983 | ... | 0987098
Any ideas?
The cleanest way I've seen so far is something along the lines of filtering out the first row
csv_rows = sc.textFile('path_to_csv')
skipable_first_row = csv_rows.first()
useful_csv_rows = csv_rows.filter(row => row != skipable_first_row)
I have a list of survey results that looks similar to the following:
| Email | Question 1 | Question 2 |
| ----------------- | ---------- | ---------- |
| test#example.com | Always | Sometimes |
| test2#example.com | Always | Always |
| test3#example.com | Sometimes | Never |
Question 1 and Question 2 (and a few others) have the same discrete set of values (from a dropdown list on the survey).
I want to show the data in the following format in Tableau (a table is fine, but a heatmap or highlight table would be best):
| | Always | Sometimes | Never |
| ---------- | ------ | --------- | ----- |
| Question 1 | 2 | 1 | 0 |
| Question 2 | 1 | 1 | 1 |
How can I achieve this? I've tried various combinations of rows and columns and I just can't seem to get close to this layout. Do I need to use a calculated value?
As far as I know - it is not natively possible with Tableau, because what you have is kind of a pivot table.
What you can do is unpivot the whole table as explained here https://stackoverflow.com/a/20543651/5130012, then you can load the data into Tableau and create the table you want.
I did some dummy data and tried it.
That's my "unpivoted" table:
Row,Column,Value
test,q1,always
test,q2,sometimes
test1,q1,sometimes
test1,q2,never
test10,q1,always
test10,q2,always
test11,q1,sometimes
test11,q2,never
And that's how it looks in Tableau: