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Questions tagged [projection]

A projection is the transformation of a set of data from one form into another.

Mathematically speaking a projection is a function that yields the same result if applied multiple times.

The term is used with this meaning in graphics when 'projecting' a 3D scene on a 2D canvas.

The same is often happening when analyzing data with many dimensions (age, gender, number of transactions, ...) and projecting it on fewer dimensions, in the simple case by just dropping dimensions or by creating new dimensions like (might commit fraud).

When dealing with typed languages the dimensions might be attributes of a class. So if I have one or multiple types with attributes (A, B, C, ...) and create from instances of those types instances of a type which has only the attributes (A, B) this is a projection too.

Another example are databases. A projection is an operation which discards some attributes of a tuple, in other words, which omits some columns of a relational database query result. For an object or document database a projection filters out some fields.

After all a database projection yields the same result if applied multiple times, too.

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MongoDB search multiple Field in multiple subDocument

My MongoDB data structure looks like this: { "id": "7118592", "passages": [ { "infons": { "article-id_pmid": "32292259", "title": "Keywords", …
Ramzi Bouchair
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UWP APP can share a child window in different monitor?

I'm trying to show two windows on two monitors, I already checked ProjectionManager only support to sent windows (app views) to secondary displays, and swaps main and projection views. But I want to share a child window in two monitors, can I do…
jerry
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OpenGL: How does perspective division work?

After multiplication by the projection matrix If any clip coordinate is less than -wc, or greater than wc, then the vertex will be discarded. Then perspective division is performed by W. But what happens if w = 0? OpenGL just doesn't do division?
AProgTV
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How to transform EPSG:6249 coordinates to "standard" lat/lon coordinates?

I have a set of coordinate points in a format refer to as "MAGNA-SIRGAS / Cali urban grid" or "EPSG:6249". Each point coordinates are labeled as North and East. I would like to transform the coordinates to WGS84 (EPSG:4326) coordinates. I have tried…
user404332
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How to render points on a 2D horizontal (Oxy) plane into points on a 2D vertical (phone) plane?

I'm trying to convert (longitude/latitude) locations to rectangles on a phone screen. But for now let's pretend they're normal points on Oxy plane. Assume the camera is standing at point (X,Y), corresponing to the center of the phone screen. It's…
Duke Le
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QueryDsl Projections leave a field blank

@Entity public class DocumentConsolidated { @Id private UUID id; @OneToOne(fetch = FetchType.EAGER, optional = false, cascade = CascadeType.ALL) @JoinColumn(name = "metadata_id") private DocumentMetadata documentMetadata; …
NicolaeS
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MongoDB : Group by rounded value

Let's take an example : { _id: "xx", total: 12345, name: "Bob" } { _id: "xa", total: 123, name: "Bob" } { _id: "xb", total: 1290, name: "Bob" } { _id: "xc", total: 1255, name: "Bob" } I would like to have something like : [ { name: '100', count:…
Zozor
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Output of projectPoints() function

i used projectPoints() function of OpenCV to do projection from world coordinates to pixel coordinates, the output image points are vector point2f, how can I extract the x,y coordinates from imagePoints? seconde question, some of the imagePoints are…
Hosein shirali
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Mongo DB project elements of an array into a single array

I have a collection in my DB where each item looks like this : { "_id" : ObjectId("XXXXXX"), "name" : "foo", "products" : [{ "name" : "bar", "code" : 123 },{ "name" : "foo", "code" : 321 }] } And I want to get…
Matias Barrios
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Halcon - Shift coordinates to a different plane

I have coordinates (X/Y) that are relative to a specific Plane on a pose. I would need to know how the Y value changes, if the Point would be projected to another Plane from the camera's view, that is located 10 mm further away in Z direction. The…
sharkyenergy
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ProjectionOperation plus and previousOperation Aggregation mongodb java

Aggregation aggregation = newAggregation( match(Criteria.where("moment").gte(from).lte(to)), project("pass", "carrier", "route", "iso").and("iso").as("country") .and("$moment").plus(14400000).as("shifted"), …
sd.3391519
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How to keep same extent?

I have 10 raster files. I want to stack them. How to keep same extent for all these 10 files ? library(raster) rasterfile <- list.files(file.path("E:/NDVI RESULT FINAL"), full.names = T, pattern = '.tif$') f1 <- "E:/NDVI RESULT FINAL/NDVI…
Ali Rawail
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Project lat/long to pixels

I´m making an app for smartwatches, where I need to draw the track user is currently using. The track consists of lat/long pairs. So far I´ve tried many functions, but with this one below I got most consistent results yet there are tracks, that got…
Leticek
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Mongo create field with merge of 2 arrays of same collection (like Left join in relational)

I have a collection that has 2 arrays inside. One has fewer props than other, but both are linked by prop 'Code'. I would like to project a 3rd array that would be the merge of both, but they must be distinct. An example: [ { 'PartnerName':…
2Fast4YouBR
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MongoDB Aggregation - $filter in projection for embedded arrays

I have a complex structure of JSON object which contain (N) number of embedded arrays. A single entry is an object with two fields : @name and content. I need to filter them in projection stage (without using $unwind) to get one specific object…
Hubert Stasiuk
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