projection

问题 Is there a way to project fields that may or may not exist? Such as having it defined as null or undefined? For instance, I am doing a query with: $project: { date: 1, name: "$person.name", age: "$person.age" } Not all documents are guaranteed to have a $person.age, but instead of the ones without an age being returned as { date: Today, name: "Bill" }, I would like it to say { date: Today, name: "Bill", age: null }. Or something similar. Is there a better way than just iterating through the

问题 I'm using D3 to draw some pieces of information on canvas. And I got my aim in version 3 but failed in version 4 (Of course, I had changed the updated functions in version 4 such as d3.geo.mercator() to d3.geoMercator() ). I debugged some relative functions and found the projection function was different. In Version 3: function projection(point) { point = projectRotate(point[0] * d3_radians, point[1] * d3_radians); return [ point[0] * k + δx, δy - point[1] * k ]; } In Version 4: function

问题 I've been hitting my head against the wall because my Google App Engine python project has a very simple NDB projection query which works fine on my local machine, but mysteriously fails when deployed to production. Adding to the mystery... as a test I added an identical projection on another property, and it works in both dev and production! Could anyone help please?! Here are more details: I have the following entity that represents an expense: class Entry(ndb.Model): datetime = ndb

问题 My NetCDF file has 4 dimensions (longitude, latitude, time, level pressure) and several variables. I want to replace the longitude data which is [340 342 344 ... 360 0 2 4 ... 18 20] by [-20 -18 -16 ... -2 0 2 4 ... 18 20]. In fact the longitude is counted from 0° to 360° but I need to have it from -180° to 180°. I have found some ideas on Internet but I don't know how to apply them. Here an explanation: "Some netcdf files contain strictly positive values [0,360] which are not compatible with

问题 I'm still implementing a perspective projection for my augmented reality application. I've already asked some questions about the viewport-calculation and other camera stuff, which is explained from Aldream in this thread However, I don't get any useful value at the moment and I think this depends on my calculation of the cartesian coordinate space. I had some different ways to transform latitude,longitude and altitude to a cartesian coordinate space, but nothing of them seems to work

问题 I have a Spring MVC/Spring Data / Mongo DB application. I have setted up my environement according the the spring data documentation and my repositories work fine (I can execute queries with predicates) I was wondering if it was possible to execute a type safe query (using Spring Data and QueryDSL) while making a projection (I want only a few fields of a very big document). The QueryDSL documentation gives an example for Hibernate but states it can be done in all modules QueryDSL

问题 I am trying to perform a projection query in order to fetch several properties from each entity in my datastore of over ten thousand entities. I have read and followed the documentation, but my query is not returning any results. I've even simplified my projection down to only projecting a single property, the entity's ID field, but still get 0 results. Here is my simplified code: Query q = new Query("MyEntity"); q.addProjection(new PropertyProjection("entityId", Long.class));

问题 I have a domain object, Expense, that has a field called initialFields . It's annotated as so: @OneToMany(fetch = FetchType.EAGER, cascade = { CascadeType.ALL }, orphanRemoval = true) @JoinTable(blah blah) private final List<Field> initialFields; Now I'm trying to use Projections in order to only pull certain fields for performance reasons, but when doing so the initialFields field is always null. It's the only OneToMany field and the only field I am trying to retrieve with the projection

问题 I have a domain object, Expense, that has a field called initialFields . It's annotated as so: @OneToMany(fetch = FetchType.EAGER, cascade = { CascadeType.ALL }, orphanRemoval = true) @JoinTable(blah blah) private final List<Field> initialFields; Now I'm trying to use Projections in order to only pull certain fields for performance reasons, but when doing so the initialFields field is always null. It's the only OneToMany field and the only field I am trying to retrieve with the projection

问题 I am looking at the kitti dataset and particularly how to convert a world point into the image coordinates. I looked at the README and it says below that I need to transform to camera coordinates first then multiply by the projection matrix. I have 2 questions, coming from a non computer vision background I looked at the numbers from calib.txt and in particular the matrix is 3x4 with non-zero values in the last column. I always thought this matrix = K[I|0] , where K is the camera's intrinsic