mitchell model - Page 31

Screening (multi)collinearity in a regression model

- by aL3xa

I hope that this one is not going to be "ask-and-answer" question... here goes: (multi)collinearity refers to extremely high correlations between predictors in the regression model. How to cure them... well, sometimes you don't need to "cure" collinearity, since it doesn't affect regression model itself, but interpretation of an effect of individual predictors. One way to spot collinearity is to put each predictor as a dependent variable, and other predictors as independent variables, determine R2, and if it's larger than .9 (or .95), we can consider predictor redundant. This is one "method"... what about other approaches? Some of them are time consuming, like excluding predictors from model and watching for b-coefficient changes - they should be noticeably different. Of course, we must always bare in mind specific context/goal of analysis... Sometimes, only remedy is to repeat a research, but right now, I'm interested in various ways of screening redundant predictors when (multi)collinearity occurs in a regression model.

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Accessing controller methods inside a model with Kohana/MVC Framework

- by eth0

Hi all, I need to able to access controller methods from a model using the Kohana V2.3 framework. At the moment I'm passing the controller object (by ref.) to the model on creation which works perfectly fine but I can't help think there is a more "cleaner" way - does anybody have any suggestions? Would Kohana V3 resolve this with its HMVC pattern? This may help: http://www.ifc0nfig.com/accessing-the-calling-controller-in-a-model-within-kohana/

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A view model mvvm design issue

- by Chen Kinnrot

the best way to explain is with example so: this is the model public class Person { public int age; public string name; } this is the view model public class PersonVM { } my question is: should the vm expose the person to the datga template or encapsulate the model properties with his own properties?

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Associate model class with entire row in JTable

- by kilonet

How can I associate my model class with entire row in JTable in order to get link to model class by row number?

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how to model a follower stream in appengine?

- by molicule

I am trying to design tables to buildout a follower relationship. Say I have a stream of 140char records that have user, hashtag and other text. Users follow other users, and can also follow hashtags. I am outlining the way I've designed this below, but there are two limitaions in my design. I was wondering if others had smarter ways to accomplish the same goal. The issues with this are The list of followers is copied in for each record If a new follower is added or one removed, 'all' the records have to be updated. The code class HashtagFollowers(db.Model): """ This table contains the followers for each hashtag """ hashtag = db.StringProperty() followers = db.StringListProperty() class UserFollowers(db.Model): """ This table contains the followers for each user """ username = db.StringProperty() followers = db.StringListProperty() class stream(db.Model): """ This table contains the data stream """ username = db.StringProperty() hashtag = db.StringProperty() text = db.TextProperty() def save(self): """ On each save all the followers for each hashtag and user are added into a another table with this record as the parent """ super(stream, self).save() hfs = HashtagFollowers.all().filter("hashtag =", self.hashtag).fetch(10) for hf in hfs: sh = streamHashtags(parent=self, followers=hf.followers) sh.save() ufs = UserFollowers.all().filter("username =", self.username).fetch(10) for uf in ufs: uh = streamUsers(parent=self, followers=uf.followers) uh.save() class streamHashtags(db.Model): """ The stream record is the parent of this record """ followers = db.StringListProperty() class streamUsers(db.Model): """ The stream record is the parent of this record """ followers = db.StringListProperty() Now, to get the stream of followed hastags indexes = db.GqlQuery("""SELECT __key__ from streamHashtags where followers = 'myusername'""") keys = [k,parent() for k in indexes[offset:numresults]] return db.get(keys) Is there a smarter way to do this?

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MVC, can model save/load its data?

- by fuzzygoat

Quick question, my data model is a singleton object and it contains a list of names I want archive. My idea is to make the model responsible for loading / saving this data. The ModelLoad will then be called by the ViewControllerviewDidLoad and the ModelSave by ViewControllerapplicationWillTerminate. I could do the load / save directly within the ViewController, but this would be messy as the list of names are on instance variable of the model. gary

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Adding items to Model Collection in ASP.NET MVC

- by Stacey

In an ASP.NET MVC application where I have the following model.. public class EventViewModel { public Guid Id { get; set; } public List<Guid> Attendants { get; set; } } passed to a view... public ActionResult Create(EventViewModel model) { // ... } I want to be able to add to the "Attendants" Collection from the View. The code to add it works just fine - but how can I ensure that the View model retains the list? Is there any way to do this without saving/opening/saving etc? I am calling my addition method via jQuery $.load. public void Insert(Guid attendant) { // add the attendant to the attendees list of the model - called via $.load } I would also like to add there is no database. There is no storage persistence other than plain files.

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Screening (multi)collinearity in a reggresion model

- by aL3xa

I hope that this one is not going to be "ask-and-answer" question... here goes: (multi)collinearity refers to extremely high correlations between predictors in the regression model. How to cure them... well, sometimes you don't need to "cure" collinearity, since it doesn't affect regression model itself, but interpretation of an effect of individual predictors. One way to spot collinearity is to put each predictor as a dependent variable, and other predictors as independent variables, determine R2, and if it's larger than .9 (or .95), we can consider predictor redundant. This is one "method"... what about other approaches? Some of them are time consuming, like excluding predictors from model and watching for b-coefficient changes - they should be noticeably different. Of course, we must always bare in mind specific context/goal of analysis... Sometimes, only remedy is to repeat a research, but right now, I'm interested in various ways of screening redundant predictors when (multi)collinearity occurs in a regression model.

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How to use associated Model as datasource for DataView

- by Chris Gilbert

I have a Model structure as shown below and I want to know how to use the Bookings array as the datasource of my DataView. Model Structure: Client ClientId Name Bookings (HasManyAssociation) Contacts (HasManyAssociation) AjaxProxy JsonReader (ImplicitIncludes is set to true so child models are created with one call) Booking BookingNodeId BookingDetails Contact ContactNodeId ContactDetails The above gives me a data structure as follows: Client Bookings[ Booking Booking ] Contacts[ Contact Contact ] What I want to be able to do is either, create a Store from my Bookings array and then use that store as the datasource for my DataView OR directly use the Bookings array as the datasource (I don't really care how I do it to be honest). If I setup the AjaxProxy on my Booking model it works fine but then obviously I cannot automatically create my Client and Contacts when I load my JSON. It seems to me to make sense that the Client model, being the top level model hierarchically, is the one to load the data. EDIT: I figured it out as follows (with special thanks to handet87 below for his dataview.setStore() pointer). The key in this case is to know that creating the relationship actually sets up another store called, in this case BookingsStore and ContactsStore. All I needed to do was dataview.setStore("BookingsStore")

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getting posted values in model class in symfony

- by THOmas

How i can pass values from action class to model class

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Creating an additional related model with Devise

- by Tim Sullivan

I've started to implement a new project using Devise, which is pretty fantastic for handling users. However, when a user signs up, they're not just creating a User model, but also need to create a related Account model that represents the company. Additional users will also belongs_to this Account model. I can't seem to find a hook for this in Devise, though it seems like a pretty common pattern. What's the best practice for this?

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How to perform Rails model validation checks within model but outside of filters using ledermann-rails-settings and extensions

- by user1277160

Background I'm using ledermann-rails-settings (https://github.com/ledermann/rails-settings) on a Rails 2/3 project to extend virtually the model with certain attributes that don't necessarily need to be placed into the DB in a wide table and it's working out swimmingly for our needs. An additional reason I chose this Gem is because of the post How to create a form for the rails-settings plugin which ties ledermann-rails-settings more closely to the model for the purpose of clean form_for usage for administrator GUI support. It's a perfect solution for addressing form_for support although... Something that I'm running into now though is properly validating the dynamic getters/setters before being passed to the ledermann-rails-settings module. At the moment they are saved immediately, regardless if the model validation has actually fired - I can see through script/console that validation errors are being raised. Example For instance I would like to validate that the attribute :foo is within the range of 0..100 for decimal usage (or even a regex). I've found that with the previous post that I can use standard Rails validators (surprise, surprise) but I want to halt on actually saving any values until those are addressed - ensure that the user of the GUI has given 61.43 as a numerical value. The following code has been borrowed from the quoted post. class User < ActiveRecord::Base has_settings validates_inclusion_of :foo, :in => 0..100 def self.settings_attr_accessor(*args) >>SOME SORT OF UNLESS MODEL.VALID? CHECK HERE args.each do |method_name| eval " def #{method_name} self.settings.send(:#{method_name}) end def #{method_name}=(value) self.settings.send(:#{method_name}=, value) end " end >>END UNLESS end settings_attr_accessor :foo end Anyone have any thoughts here on pulling the state of the model at this point outside of having to put this into a before filter? The goal here is to be able to use the standard validations and avoid rolling custom validation checks for each new settings_attr_accessor that is added. Thanks!

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How to configure a has_many association with non-ActiveRecord model

- by Callmeed

My Rails app has a normal ActiveRecord "Account" model stored in the database. The model will store the URL to a remote XML file which defines some other objects. For example, the Account has_many :galleries but the Gallery model is simply defined by nodes in the XML document. So how do I get /accounts/1/galleries to show the galleries from that account's XML? How do I setup this relationship? I know how to do basic non-AR models, but I'm not sure how to define the association or if I need to create a Gallery model at all.

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How to render a text box instead of a select box when using model form set

- by iHeartDucks

Hi, When I render my formset, one of the field renders as a select box because it is a foreign field in the model. Is there a way to change this to a text input? I want to populate that field by using Ajax auto complete. Adding a widget to the modelform is not working because the modelformset_factory takes a model and not a model form.

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django model relation definition

- by Laurent Luce

Hello, Let say I have 3 models: A, B and C with the following relations. A can have many B and many C. B can have many C Is the following correct: class A(models.Model): ... class B(models.Model): ... a = ForeignKey(A) class C(models.Model): ... a = ForeignKey(A) b = ForeignKey(B)

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Custom OData operation / customize EF model to hide join table in many-to-many relationship

- by AC

I've got a data model that has two tables with a join table for a many to many relationship & creating an OData service to expose the data for CRUD ops in a Silverlight app. What I'd like to do is abstract the join table from the service. I'm not sure if the best way to do this would be in the model (using EF in .NET3.5SP1) or if I should do it with a custom service operation. If I do it in the EF model (not sure how I'd do this), then the OOTB WCF Data Service stuff would make it easy to say [..]/Courses(1)/Modules ... otherwise I'd have to create a custom operation to do this. Is it possible to do this in the EF model and if so, how does that work?

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Initialize child models at model creation

- by Antoine

I have a model Entree which belongs to a model Vin, which itself belongs to a model Producteur. On the form for Entree creation/edition, I want to allow the user to define the attributes for parent Vin and Producteur to create them, or retrieve them if they exist (retrieval based on user input). For now I do the following in Entree new and edit actions: @entree = Entree.new @entree.vin = Vin.new @entree.vin.producteur = Producteur.new and use fields_for helper in the form,and that works. But I intend to have much more dependencies with more models, so I want to keep it DRY. I defined a after_initialize callback in Vin model which does the producteur initialization: class Vin < ActiveRecord::Base after_initialize :vin_setup def vin_setup producteur = Producteur.new end end and remove the producteur.new from the controller. However, get an error on new action: undefined method `model_name' for NilClass:Class for the line in the form that says <%= fields_for @entree.vin.producteur do |producteur| %> I guess that means the after_initialize callback doesn't act as I expect it. Is there something I'm missing? Also, I get the same error if I define a after_initialize method in the Vin model instead of definiing a callback.

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Asp.Net MVC Handle Drop Down Boxes that are not part of the Model

- by Pino

I have a small form which the user must fill in and consists of the following fields. Name (Text) Value (Text) Group (Group - Is a list of option pulled from a database table) Now the Model for this View looks like so, public string Name { get; set; } public string Value { get; set; } public int GroupID { get; set; } Now the view is Strongly Typed to the above model. What method would one use to populate the drop down list? Since the data is not contained within the Model (It could be contained in the Model) should we be using Temp/View data? A HTML Helper? What would be the ideal way to achieve this.

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Django admin: how do I add an unrelated model field to a model change/add page?

- by NP

I have the following models: class Foo(models.Model): field1 = models.IntegerField() ... class Bar(models.Model): field1 = models.IntegerField() ... class Foo_bar(models.Model): foo = models.ForeignKey(Foo) bar = models.ForeignKey(Bar) ... In the admin, I want it so that in the Foo change/add page, you can specify a Bar object, and on save I want to create a Foo_bar object to represent the relationship. How can I do this through customizing the Admin site/ModelAdmins? Thanks.

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MVC Custom Model Binder Binding Multiple Values

- by BMD86

Hello everyone, I have a scenario in which I have multiple sources to bind to my model. For one, I have a view tied to a strongly-typed model, but this scenario also entails posting data to this view from a 3rd party site. Essentially, what I believe I am after in the custom model binding is to investigate the form values in the Request object within HTTPContext to see if I have a field such as "postedFirstName". If so, I want to bind that value instead of the textbox "FirstName" in my view. I've done a good bit of searching but have not find anything that exactly addresses such a scenario. This link was close, I thought, but not quite: http://stackoverflow.com/questions/970335/asp-net-mvc-mixing-custom-and-default-model-binding Any input is greatly appreciated!

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Cakephp with underscore table ignores model

- by xiaohouzi79

Hi, I have one table metrics and another table metric_levels. In the Metric model I have $hasMany = 'MetricLevels' but anything inside the MetricLevels model is totally ignored. But, if I rename the model to 'Metric' and have $useTable = 'metric_levels' it works fine. I've tried all combinations, but none seem to work. I've tried plurals, singulars, underscores, nothing seems to work. The model is simply ignored and it just takes the value from the database. Any help is appreciated.

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Passing a model into RedirectToAction()

- by larryq

I'm curious how this works. In MVC you can call View() and pass a model as a parameter, but RedirectToAction (one of its incarnations at least) takes a 'routeValues' object, which appears to be the closest match. If your model is passed in this parameter will that model type be available in the subsequent action method? Or are there caveats involved that might prevent accurate translation in some circumstances?

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Updating database row from model

- by Jamie Dixon

Hey everyone, I'm haing a few problems updating a row in my database using Linq2Sql. Inside of my model I have two methods for updating and saving from my controller, which in turn receives an updated model from my view. My model methods like like: public void Update(Activity activity) { _db.Activities.InsertOnSubmit(activity); } public void Save() { _db.SubmitChanges(); } and the code in my Controller likes like: [HttpPost] public ActionResult Edit(Activity activity) { if (ModelState.IsValid) { UpdateModel<Activity>(activity); _activitiesModel.Update(activity); _activitiesModel.Save(); } return View(activity); } The problem I'm having is that this code inserts a new entry into the database, even though the model item i'm inserting-on-submit contains a primary key field. I've also tried re-attaching the model object back to the data source but this throws an error because the item already exists. Any pointers in the right direction will be greatly appreciated. UPDATE: I'm using dependancy injection to instantiate my datacontext object as follows: IMyDataContext _db; public ActivitiesModel(IMyDataContext db) { _db = db; }

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ModelName(django.contrib.auth.models.User) vs ModelName(models.Model)

- by amr.negm

I am developing a django project. I created some apps, some of those are related to User model, for instance, I have a feeds app that handles user feeds, and another app that deals with extra user data like age, contacts, and friends. for each of these, I created a table that should be connected to the User model, which I using for storing and authenticating users. I found two ways to deal with this issue. One, is through extending User model to be like this: ModelName(User): friends = models.ManyToMany('self') ..... Two, is through adding a foreign key to the new table like this: ModelName(models.Model): user = models.ForeignKey(User, unique=True) friends = friends = models.ManyToMany('self') ...... I can't decide which to use in which case. in other words, what are the core differences between both?

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Pass existing model into AJAX PartialViewResult

- by Joe

I’m using AJAX to asynchronously update a partial view and need to pass the existing model into the partial view. Controller Action public ActionResult Edit(int id) { var vM = new MyViewModel(); // vM is viewModel return View(vM); } Edit View @using (Html.BeginForm()) { @Html.ValidationSummary(true) ... @Html.Partial("AJAX_Views/_Ship") _Ship Partial View @model MyProject.ViewModels.MyViewModel <table class="detailtable" style="min-width:398px"> <tr> <th style="padding-left:132px" colspan="2"> Shipping       Address @Ajax.ActionLink("Delete", "SHIPDEL", new AjaxOptions { UpdateTargetId = "Ship", InsertionMode = InsertionMode.Replace, HttpMethod = "Get" }) <tr><th style="min-width:152px">Street:</th> @Html.HiddenFor(m => m.CmpAdrsSh.Id) @Html.HiddenFor(m => m.CmpAdrsSh.CompPersonId) @Html.HiddenFor(m => m.CmpAdrsSh.IsShip) <td>@Html.EditorFor(m => m.CmpAdrsSh.Street) @Html.ValidationMessageFor(m => m.CmpAdrsSh.Street) </td></tr> <tr><th>City:</th> <td>@Html.EditorFor(m => m.CmpAdrsSh.City) @Html.ValidationMessageFor(m => m.CmpAdrsSh.City) </td></tr> <tr><th>State:</th> <td>@Html.DropDownList("CmpAdrsSh.State", (IEnumerable<SelectListItem>)ViewBag._State) @Html.ValidationMessageFor(m => m.CmpAdrsSh.State) </td></tr> <tr><th>Zip:</th> <td>@Html.EditorFor(m => m.CmpAdrsSh.Zip) @Html.ValidationMessageFor(m => m.CmpAdrsSh.Zip) </td></tr> _ShipDel Partial View @model MyProject.ViewModels.MyViewModel <table class="detailtable" style="min-width:398px"> <tr> <th style="padding-left:132px" colspan="2"> Shipping       Address Marked for Deletion.</th></tr> <tr><td>To not Delete Select Cancel below!</td></tr> @Html.HiddenFor(m => m.CmpAdrsSh.Street) @Html.HiddenFor(m => m.CmpAdrsSh.City) @Html.HiddenFor(m => m.CmpAdrsSh.State) @Html.HiddenFor(m => m.CmpAdrsSh.Zip) Controller PartialViewResult Action public PartialViewResult SHIPDEL() { return PartialView("AJAX_Views/_ShipDel"); } I tried adding this.ModelState to the Action but then the view will not render. I'm guessing I somehow have to pass the model to the SHIPDEL Action first. I couldn't find an @Ajax.ActionLink overload that would allow this. public PartialViewResult SHIPDEL() { return PartialView("AJAX_Views/_ShipDel", this.ModelState); } In the _ShipDel Partial View I need to expose the CmpAdrsSh properties so the model validates in the POST Action. The model is empty at this point. How do I pass the existing vM model into the _ShipDel partial view? Thank you,

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- by aL3xa

- by eth0

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- by kilonet

- by molicule

- by fuzzygoat

- by Stacey

- by aL3xa

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