- Dependency sources
- Version constraints
Caret is an R package for classification and regression training. It provides a standardized interface to several of R's machine learning packages, along with utilities for training and plotting.%% plyr::revalue(c('0'='control', '1'='case')). R r-caret glmnet coefficients. Asked Oct 5 at 12:16. 454 2 2 silver badges 13 13 bronze. For example ^1.2.3 is equivalent to =1.2.3 0.0 as none of the releases until 2.0 should break backwards compatibility. For pre-1.0 versions it also acts with safety in mind and treats ^0.3 as =0.3.0 0.4.0. This is the recommended operator for maximum interoperability when writing library code. Example: ^1.2.3: caret sign is: answer.
Caret Commands We use cookies to optimally design and continuously improve our websites for you, as well as to display news, articles and advertisements in line with your interests. We'll assume you're ok with this, but you can opt-out if you wish. This blog post series is on machine learning with R. We will use the Caret package in R. In this part, we will first perform exploratory Data Analysis (EDA) on a real-world dataset, and then apply non-regularized linear regression to solve a supervised regression problem on the dataset. We will predict power output given a. 5.5.1 Pre-Processing Options. As previously mentioned,train can pre-process the data in various ways prior to model fitting. The function preProcess is automatically used. This function can be used for centering and scaling, imputation (see details below), applying the spatial sign transformation and feature extraction via principal component analysis or independent component analysis.
Dependencies are one of the core concepts of the pub package manager.A dependency is another package that your package needs in order to work.Dependencies are specified in your pubspec.You list only immediate dependencies — thesoftware that your package uses directly. Pub handlestransitive dependencies for you.
Borisfx mocha. This page has detailed information on how to specify dependencies.At the end is a list ofbest practices for package dependencies.
Overview
For each dependency, you specify the name of the package you depend onand the range of versions of that package that you allow.You can also specify thesource,which tells pub how to locate the package,and any additional description that the source needs to find the package.
Here is an example of specifying a dependency:
This YAML code creates a dependency on the
transmogrify
packageusing the default source (pub.dev) andallowing any version from 1.0.0
to 2.0.0
(but not including 2.0.0
).See the version constraintssection of this page for syntax details.If you want to specify a source, the syntax looks a bit different:
This YAML code creates a dependency on the
transmogrify
packageusing the hosted
source.Everything under the source key (here, just a map with a url:
key)is the description that gets passed to the source.Each source has its own description format,which is described in the dependency sources sectionof this page.The version constraint is optional but recommended.Use this long form when you don’t use the default source or when you have acomplex description that you need to specify.But in most cases, you’ll just use the simple
packagename: version
form.Dependency sources
Pub can use the following sources to locate packages:
SDK
The SDK source is used for any SDKs that are shipped along with packages,which may themselves be dependencies.Currently, Flutter is the only SDK that is supported.
The syntax looks like this:
The identifier after
sdk:
indicates which SDK the package comes from.If it’s flutter
, the dependency is satisfiable as long as:- Pub is running in the context of the
flutter
executable - The Flutter SDK contains a package with the given name
- That package’s version matches the version constraint
![Caret 1 1 0 m Caret 1 1 0 m](https://img.buzzfeed.com/buzzfeed-static/static/campaign_images/webdr02/2013/1/8/0/taylor-swift-sad-and-alone-on-a-boat-1-10292-1357621241-2_big.jpg)
If it’s an unknown identifier, the dependency is always considered unsatisfied.
A package with an
sdk
dependencymust have a Dart SDK constraint with a minimum version of at least 1.19.0.This constraint ensures that older versions of pub won’tinstall packages that have sdk
dependencies.Hosted packages
A hosted package is one that can be downloaded from the pub.dev site(or another HTTP server that speaks the same API). Here’s an exampleof declaring a dependency on a hosted package:
This example specifies that your package depends on a hosted package named
transmogrify
and will work with any version from 1.4.0 to 2.0.0(but not 2.0.0 itself).If you want to use your own package server, you can use a description thatspecifies its URL: Tweetbot 2 3 4 – popular twitter client.
Git packages
Sometimes you live on the bleeding edge and need to use packages thathaven’t been formally released yet. Maybe your package itself is still indevelopment and is using other packages that are being developed at thesame time. To make that easier, you can depend directly on a packagestored in a Git repository.
The
git
here says this package is found using Git, and the URL after that isthe Git URL that can be used to clone the package.Even if the package repo is private, if you canconnect to the repo using SSH,then you can depend on the package by using the repo’s SSH URL:
If you want to depend on a specific commit, branch, or tag,add a
ref
argument:The ref can be anything that Git allows to identify a commit.
Pub assumes that the package is in the root of the Git repository.To specify a different location in the repo, use the
path
argument:The path is relative to the Git repo’s root.
Path packages
Sometimes you find yourself working on multiple related packages at the sametime. Maybe you are creating a framework while building an app that uses it.In those cases, during development you really want to depend on the liveversion of that package on your local file system. That way changes in onepackage are instantly picked up by the one that depends on it.
To handle that, pub supports path dependencies.
This says the root directory for
transmogrify
is /Users/me/transmogrify
.For this dependency, pub generates a symlink directly to the lib
directoryof the referenced package directory. Any changes you make to the dependentpackage are seen immediately. You don’t need to run pub every time youchange the dependent package.Relative paths are allowed and are considered relative to the directorycontaining your pubspec.
Path dependencies are useful for local development, but do not work whensharing code with the outside world—not everyone can get toyour file system. Because of this, you cannot upload a package to thepub.dev site if it has any path dependencies in its pubspec.
Instead, the typical workflow is:
- Edit your pubspec locally to use a path dependency.
- Work on the main package and the package it depends on.
- Once they’re both working, publish the dependent package.
- Change your pubspec to point to the now hosted version of its dependent.
- Publish your main package too, if you want.
Version constraints
Specifying version constraints lets peopleusing your package know which versions of its dependencies they can rely on tobe compatible with your library. Your goal is to allow a range of versions aswide as possible to give your users flexibility. But it should be narrow enoughto exclude versions that you know don’t work or haven’t been tested.
The Dart community uses semantic versioning1, which helps you know which versions should work.If you know that your package works fine with
1.2.3
of some dependency, thensemantic versioning tells you that it should work with any subsequentstable release before 2.0.0
.For details on pub’s version system,see the package versioning page.You can express version constraints using eithercaret syntax (
^1.2.3
) ortraditional syntax ('>=1.2.3 <2.0.0'
).Caret syntax
Caret syntax is a compact way of expressing the most commonsort of version constraint.
^version
means the range of all versions guaranteed to be backwardscompatible with the specified version.For example,
^1.2.3
is equivalent to '>=1.2.3 <2.0.0'
, and^0.1.2
is equivalent to '>=0.1.2 <0.2.0'
.The following is an example of caret syntax:Because caret syntax was introduced in Dart 1.8.3,it requires an SDK constraint(using traditional syntax)to ensure that older versions of pub don’t try to process it.For example:
Traditional syntax
A version constraint that uses traditional syntaxis a series of the following:
any
- The string
any
allows any version. This is equivalent to an emptyversion constraint, but is more explicit. Althoughany
is allowed,we don’t recommend it. 1.2.3
- A concrete version number pins the dependency to only allow that exact version. Avoid using this when you can because it can cause version lock for your users and make it hard for them to use your package along with other packages that also depend on it.
>=1.2.3
- Allows the given version or any greater one. You’ll typically use this.
>1.2.3
- Allows any version greater than the specified one but not thatversion itself.
<=1.2.3
- Allows any version lower than or equal to the specified one. Youwon’t typically use this.
<1.2.3
- Allows any version lower than the specified one but not thatversion itself. This is what you’ll usually use because it lets you specifythe upper version that you know does not work with your package(because it’s the first version to introduce some breaking change).
You can specify version parts as you want, and their ranges are intersectedtogether. For example,
'>=1.2.3 <2.0.0'
allows any version from 1.2.3
to2.0.0
excluding 2.0.0
itself. An easier way to express this range isby using caret syntax, or ^1.2.3
.If the
>
character is in the version constraint,be sure to quote the constraint string,so the character isn’t interpreted as YAML syntax.For example, never use >=1.2.3 <2.0.0
;instead, use '>=1.2.3 <2.0.0'
or ^1.2.3
.Dev dependencies
Pub supports two flavors of dependencies: regular dependencies and devdependencies. Dev dependencies differ from regular dependencies in that devdependencies of packages you depend on are ignored. Here’s an example:
Say the
transmogrify
package uses the test
package in its tests and onlyin its tests. If someone just wants to use transmogrify
—import itslibraries—it doesn’t actually need test
. In this case, it specifiestest
as a dev dependency. Its pubspec will have something like:Pub gets every package that your package depends on, and everything thosepackages depend on, transitively. It also gets your package’s dev dependencies,but it ignores the dev dependencies of any dependent packages. Pub only getsyour package’s dev dependencies. So when your package depends on
transmogrify
it will get transmogrify
but not test
.The rule for deciding between a regular or dev dependency is simple: Ifthe dependency is imported from something in your
lib
or bin
directories,it needs to be a regular dependency. If it’s only imported from test
,example
, etc. it can and should be a dev dependency.Using dev dependencies makes dependency graphs smaller. That makes
pub
runfaster, and makes it easier to find a set of package versions that satisfies allconstraints.Dependency overrides
You can use
dependency_overrides
to temporarily override all referencesto a dependency.For example, perhaps you are updating a local copy of transmogrify, apublished library package. Transmogrify is used by other packages in yourdependency graph, but you don’t want to clone each package locallyand change each pubspec to test your local copy of transmogrify.
In this situation, you can override the dependency using
dependency_overrides
to specify the directory holding the localcopy of the package.The pubspec would look something like the following:
When you run
pub get
or pub upgrade
,the pubspec’s lockfile is updated to reflect thenew path to your dependency and, wherever transmogrify is used, pubuses the local version instead.You can also use
dependency_overrides
to specify a particularversion of a package:Warning: Using a dependency override involves some risk. For example, using an override to specify a version outside the range that the package claims to support, or using an override to specify a local copy of a package that has unexpected behaviors, may break your application.
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Best practices
It’s important to actively manage your dependencies andensure that your packages use the freshest versions possible.If any dependency is stale,then you might have not only a stale version of that package,but also stale versions of other packages in your dependency graph thatdepend on that package.These stale versions can have a negative impact onthe stability, performance, and quality of apps.
We recommend the following best practices for package dependencies:
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- Use caret syntax
- Specifying dependencies with version ranges is such as
^1.6.3
is a good practice because it allows the pub tool toselect newer versions of the package when they become available.Also, it places an upper limit on the allowed version,based on an assumption that packages use semantic versions,where any version of path versioned1.x
is compatible,but where a new version2.x
would be a major upgradethat isn’t semantically compatible with1.x
versions. - Depend on the latest stable package versions
- Use
pub upgrade
to update to the latest package versionsthat your pubspec allows.To identify dependencies in your app or package thataren’t on the latest stable versions,usepub outdated
. - Test whenever you update package dependencies
- If you run
pub upgrade
without updating your pubspec,the API should stay the sameand your code should run as before — but test to make sure.If you modify the pubspec and update to a new major version,then you might encounter breaking changes,so you need to test even more thoroughly.
[1] Pub follows version
2.0.0-rc.1
of thesemantic versioning specificationbecause that version allows packages to use build identifiers (+12345
)to differentiate versions. ↩