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Zabbix is an Enterprise Class Monitoring Solution which has the ability to scale very easily.
It allows you to monitor and collect data from thousands (even millions) of devices, applications, and even from Cloud services and more.
In this video we show you what Zabbix is, where it is used, how it is used, how to download it, how to install it on Ubuntu 20.04, and towards the end of the video we gave a brief overview of Zabbix.
⏰TIMESTAMPS⏰
#zabbix #ubuntu
1599097440
A famous general is thought to have said, “A good sketch is better than a long speech.” That advice may have come from the battlefield, but it’s applicable in lots of other areas — including data science. “Sketching” out our data by visualizing it using ggplot2 in R is more impactful than simply describing the trends we find.
This is why we visualize data. We visualize data because it’s easier to learn from something that we can see rather than read. And thankfully for data analysts and data scientists who use R, there’s a tidyverse package called ggplot2 that makes data visualization a snap!
In this blog post, we’ll learn how to take some data and produce a visualization using R. To work through it, it’s best if you already have an understanding of R programming syntax, but you don’t need to be an expert or have any prior experience working with ggplot2
#data science tutorials #beginner #ggplot2 #r #r tutorial #r tutorials #rstats #tutorial #tutorials
1652543820
Background Fetch is a very simple plugin which attempts to awaken an app in the background about every 15 minutes, providing a short period of background running-time. This plugin will execute your provided callbackFn
whenever a background-fetch event occurs.
There is no way to increase the rate which a fetch-event occurs and this plugin sets the rate to the most frequent possible — you will never receive an event faster than 15 minutes. The operating-system will automatically throttle the rate the background-fetch events occur based upon usage patterns. Eg: if user hasn't turned on their phone for a long period of time, fetch events will occur less frequently or if an iOS user disables background refresh they may not happen at all.
:new: Background Fetch now provides a scheduleTask
method for scheduling arbitrary "one-shot" or periodic tasks.
scheduleTask
seems only to fire when the device is plugged into power.stopOnTerminate: false
for iOS.@config enableHeadless
)⚠️ If you have a previous version of react-native-background-fetch < 2.7.0
installed into react-native >= 0.60
, you should first unlink
your previous version as react-native link
is no longer required.
$ react-native unlink react-native-background-fetch
yarn
$ yarn add react-native-background-fetch
npm
$ npm install --save react-native-background-fetch
react-native >= 0.60
react-native >= 0.60
ℹ️ This repo contains its own Example App. See /example
import React from 'react';
import {
SafeAreaView,
StyleSheet,
ScrollView,
View,
Text,
FlatList,
StatusBar,
} from 'react-native';
import {
Header,
Colors
} from 'react-native/Libraries/NewAppScreen';
import BackgroundFetch from "react-native-background-fetch";
class App extends React.Component {
constructor(props) {
super(props);
this.state = {
events: []
};
}
componentDidMount() {
// Initialize BackgroundFetch ONLY ONCE when component mounts.
this.initBackgroundFetch();
}
async initBackgroundFetch() {
// BackgroundFetch event handler.
const onEvent = async (taskId) => {
console.log('[BackgroundFetch] task: ', taskId);
// Do your background work...
await this.addEvent(taskId);
// IMPORTANT: You must signal to the OS that your task is complete.
BackgroundFetch.finish(taskId);
}
// Timeout callback is executed when your Task has exceeded its allowed running-time.
// You must stop what you're doing immediately BackgroundFetch.finish(taskId)
const onTimeout = async (taskId) => {
console.warn('[BackgroundFetch] TIMEOUT task: ', taskId);
BackgroundFetch.finish(taskId);
}
// Initialize BackgroundFetch only once when component mounts.
let status = await BackgroundFetch.configure({minimumFetchInterval: 15}, onEvent, onTimeout);
console.log('[BackgroundFetch] configure status: ', status);
}
// Add a BackgroundFetch event to <FlatList>
addEvent(taskId) {
// Simulate a possibly long-running asynchronous task with a Promise.
return new Promise((resolve, reject) => {
this.setState(state => ({
events: [...state.events, {
taskId: taskId,
timestamp: (new Date()).toString()
}]
}));
resolve();
});
}
render() {
return (
<>
<StatusBar barStyle="dark-content" />
<SafeAreaView>
<ScrollView
contentInsetAdjustmentBehavior="automatic"
style={styles.scrollView}>
<Header />
<View style={styles.body}>
<View style={styles.sectionContainer}>
<Text style={styles.sectionTitle}>BackgroundFetch Demo</Text>
</View>
</View>
</ScrollView>
<View style={styles.sectionContainer}>
<FlatList
data={this.state.events}
renderItem={({item}) => (<Text>[{item.taskId}]: {item.timestamp}</Text>)}
keyExtractor={item => item.timestamp}
/>
</View>
</SafeAreaView>
</>
);
}
}
const styles = StyleSheet.create({
scrollView: {
backgroundColor: Colors.lighter,
},
body: {
backgroundColor: Colors.white,
},
sectionContainer: {
marginTop: 32,
paddingHorizontal: 24,
},
sectionTitle: {
fontSize: 24,
fontWeight: '600',
color: Colors.black,
},
sectionDescription: {
marginTop: 8,
fontSize: 18,
fontWeight: '400',
color: Colors.dark,
},
});
export default App;
In addition to the default background-fetch task defined by BackgroundFetch.configure
, you may also execute your own arbitrary "oneshot" or periodic tasks (iOS requires additional Setup Instructions). However, all events will be fired into the Callback provided to BackgroundFetch#configure
:
scheduleTask
on iOS seems only to run when the device is plugged into power.scheduleTask
on iOS are designed for low-priority tasks, such as purging cache files — they tend to be unreliable for mission-critical tasks. scheduleTask
will never run as frequently as you want.fetch
event is much more reliable and fires far more often.scheduleTask
on iOS stop when the user terminates the app. There is no such thing as stopOnTerminate: false
for iOS.// Step 1: Configure BackgroundFetch as usual.
let status = await BackgroundFetch.configure({
minimumFetchInterval: 15
}, async (taskId) => { // <-- Event callback
// This is the fetch-event callback.
console.log("[BackgroundFetch] taskId: ", taskId);
// Use a switch statement to route task-handling.
switch (taskId) {
case 'com.foo.customtask':
print("Received custom task");
break;
default:
print("Default fetch task");
}
// Finish, providing received taskId.
BackgroundFetch.finish(taskId);
}, async (taskId) => { // <-- Task timeout callback
// This task has exceeded its allowed running-time.
// You must stop what you're doing and immediately .finish(taskId)
BackgroundFetch.finish(taskId);
});
// Step 2: Schedule a custom "oneshot" task "com.foo.customtask" to execute 5000ms from now.
BackgroundFetch.scheduleTask({
taskId: "com.foo.customtask",
forceAlarmManager: true,
delay: 5000 // <-- milliseconds
});
API Documentation
@param {Integer} minimumFetchInterval [15]
The minimum interval in minutes to execute background fetch events. Defaults to 15
minutes. Note: Background-fetch events will never occur at a frequency higher than every 15 minutes. Apple uses a secret algorithm to adjust the frequency of fetch events, presumably based upon usage patterns of the app. Fetch events can occur less often than your configured minimumFetchInterval
.
@param {Integer} delay (milliseconds)
ℹ️ Valid only for BackgroundFetch.scheduleTask
. The minimum number of milliseconds in future that task should execute.
@param {Boolean} periodic [false]
ℹ️ Valid only for BackgroundFetch.scheduleTask
. Defaults to false
. Set true to execute the task repeatedly. When false
, the task will execute just once.
@config {Boolean} stopOnTerminate [true]
Set false
to continue background-fetch events after user terminates the app. Default to true
.
@config {Boolean} startOnBoot [false]
Set true
to initiate background-fetch events when the device is rebooted. Defaults to false
.
❗ NOTE: startOnBoot
requires stopOnTerminate: false
.
@config {Boolean} forceAlarmManager [false]
By default, the plugin will use Android's JobScheduler
when possible. The JobScheduler
API prioritizes for battery-life, throttling task-execution based upon device usage and battery level.
Configuring forceAlarmManager: true
will bypass JobScheduler
to use Android's older AlarmManager
API, resulting in more accurate task-execution at the cost of higher battery usage.
let status = await BackgroundFetch.configure({
minimumFetchInterval: 15,
forceAlarmManager: true
}, async (taskId) => { // <-- Event callback
console.log("[BackgroundFetch] taskId: ", taskId);
BackgroundFetch.finish(taskId);
}, async (taskId) => { // <-- Task timeout callback
// This task has exceeded its allowed running-time.
// You must stop what you're doing and immediately .finish(taskId)
BackgroundFetch.finish(taskId);
});
.
.
.
// And with with #scheduleTask
BackgroundFetch.scheduleTask({
taskId: 'com.foo.customtask',
delay: 5000, // milliseconds
forceAlarmManager: true,
periodic: false
});
@config {Boolean} enableHeadless [false]
Set true
to enable React Native's Headless JS mechanism, for handling fetch events after app termination.
index.js
(MUST BE IN index.js
):import BackgroundFetch from "react-native-background-fetch";
let MyHeadlessTask = async (event) => {
// Get task id from event {}:
let taskId = event.taskId;
let isTimeout = event.timeout; // <-- true when your background-time has expired.
if (isTimeout) {
// This task has exceeded its allowed running-time.
// You must stop what you're doing immediately finish(taskId)
console.log('[BackgroundFetch] Headless TIMEOUT:', taskId);
BackgroundFetch.finish(taskId);
return;
}
console.log('[BackgroundFetch HeadlessTask] start: ', taskId);
// Perform an example HTTP request.
// Important: await asychronous tasks when using HeadlessJS.
let response = await fetch('https://reactnative.dev/movies.json');
let responseJson = await response.json();
console.log('[BackgroundFetch HeadlessTask] response: ', responseJson);
// Required: Signal to native code that your task is complete.
// If you don't do this, your app could be terminated and/or assigned
// battery-blame for consuming too much time in background.
BackgroundFetch.finish(taskId);
}
// Register your BackgroundFetch HeadlessTask
BackgroundFetch.registerHeadlessTask(MyHeadlessTask);
@config {integer} requiredNetworkType [BackgroundFetch.NETWORK_TYPE_NONE]
Set basic description of the kind of network your job requires.
If your job doesn't need a network connection, you don't need to use this option as the default value is BackgroundFetch.NETWORK_TYPE_NONE
.
NetworkType | Description |
---|---|
BackgroundFetch.NETWORK_TYPE_NONE | This job doesn't care about network constraints, either any or none. |
BackgroundFetch.NETWORK_TYPE_ANY | This job requires network connectivity. |
BackgroundFetch.NETWORK_TYPE_CELLULAR | This job requires network connectivity that is a cellular network. |
BackgroundFetch.NETWORK_TYPE_UNMETERED | This job requires network connectivity that is unmetered. Most WiFi networks are unmetered, as in "you can upload as much as you like". |
BackgroundFetch.NETWORK_TYPE_NOT_ROAMING | This job requires network connectivity that is not roaming (being outside the country of origin) |
@config {Boolean} requiresBatteryNotLow [false]
Specify that to run this job, the device's battery level must not be low.
This defaults to false. If true, the job will only run when the battery level is not low, which is generally the point where the user is given a "low battery" warning.
@config {Boolean} requiresStorageNotLow [false]
Specify that to run this job, the device's available storage must not be low.
This defaults to false. If true, the job will only run when the device is not in a low storage state, which is generally the point where the user is given a "low storage" warning.
@config {Boolean} requiresCharging [false]
Specify that to run this job, the device must be charging (or be a non-battery-powered device connected to permanent power, such as Android TV devices). This defaults to false.
@config {Boolean} requiresDeviceIdle [false]
When set true, ensure that this job will not run if the device is in active use.
The default state is false: that is, the for the job to be runnable even when someone is interacting with the device.
This state is a loose definition provided by the system. In general, it means that the device is not currently being used interactively, and has not been in use for some time. As such, it is a good time to perform resource heavy jobs. Bear in mind that battery usage will still be attributed to your application, and shown to the user in battery stats.
Method Name | Arguments | Returns | Notes |
---|---|---|---|
configure | {FetchConfig} , callbackFn , timeoutFn | Promise<BackgroundFetchStatus> | Configures the plugin's callbackFn and timeoutFn . This callback will fire each time a background-fetch event occurs in addition to events from #scheduleTask . The timeoutFn will be called when the OS reports your task is nearing the end of its allowed background-time. |
scheduleTask | {TaskConfig} | Promise<boolean> | Executes a custom task. The task will be executed in the same Callback function provided to #configure . |
status | callbackFn | Promise<BackgroundFetchStatus> | Your callback will be executed with the current status (Integer) 0: Restricted , 1: Denied , 2: Available . These constants are defined as BackgroundFetch.STATUS_RESTRICTED , BackgroundFetch.STATUS_DENIED , BackgroundFetch.STATUS_AVAILABLE (NOTE: Android will always return STATUS_AVAILABLE ) |
finish | String taskId | Void | You MUST call this method in your callbackFn provided to #configure in order to signal to the OS that your task is complete. iOS provides only 30s of background-time for a fetch-event -- if you exceed this 30s, iOS will kill your app. |
start | none | Promise<BackgroundFetchStatus> | Start the background-fetch API. Your callbackFn provided to #configure will be executed each time a background-fetch event occurs. NOTE the #configure method automatically calls #start . You do not have to call this method after you #configure the plugin |
stop | [taskId:String] | Promise<boolean> | Stop the background-fetch API and all #scheduleTask from firing events. Your callbackFn provided to #configure will no longer be executed. If you provide an optional taskId , only that #scheduleTask will be stopped. |
BGTaskScheduler
API for iOS 13+[||]
button to initiate a Breakpoint.(lldb)
, paste the following command (Note: use cursor up/down keys to cycle through previously run commands):e -l objc -- (void)[[BGTaskScheduler sharedScheduler] _simulateLaunchForTaskWithIdentifier:@"com.transistorsoft.fetch"]
[ > ]
button to continue. The task will execute and the Callback function provided to BackgroundFetch.configure
will receive the event.BGTaskScheduler
api supports simulated task-timeout events. To simulate a task-timeout, your fetchCallback
must not call BackgroundFetch.finish(taskId)
:let status = await BackgroundFetch.configure({
minimumFetchInterval: 15
}, async (taskId) => { // <-- Event callback.
// This is the task callback.
console.log("[BackgroundFetch] taskId", taskId);
//BackgroundFetch.finish(taskId); // <-- Disable .finish(taskId) when simulating an iOS task timeout
}, async (taskId) => { // <-- Event timeout callback
// This task has exceeded its allowed running-time.
// You must stop what you're doing and immediately .finish(taskId)
print("[BackgroundFetch] TIMEOUT taskId:", taskId);
BackgroundFetch.finish(taskId);
});
e -l objc -- (void)[[BGTaskScheduler sharedScheduler] _simulateExpirationForTaskWithIdentifier:@"com.transistorsoft.fetch"]
BackgroundFetch
APIDebug->Simulate Background Fetch
$ adb logcat
:$ adb logcat *:S ReactNative:V ReactNativeJS:V TSBackgroundFetch:V
21+
:$ adb shell cmd jobscheduler run -f <your.application.id> 999
<21
, simulate a "Headless JS" event with (insert <your.application.id>)$ adb shell am broadcast -a <your.application.id>.event.BACKGROUND_FETCH
Download Details:
Author: transistorsoft
Source Code: https://github.com/transistorsoft/react-native-background-fetch
License: MIT license
1596728880
In this tutorial we’ll learn how to begin programming with R using RStudio. We’ll install R, and RStudio RStudio, an extremely popular development environment for R. We’ll learn the key RStudio features in order to start programming in R on our own.
If you already know how to use RStudio and want to learn some tips, tricks, and shortcuts, check out this Dataquest blog post.
[tidyverse](https://www.dataquest.io/blog/tutorial-getting-started-with-r-and-rstudio/#tve-jump-173bb26184b)
Packages[tidyverse](https://www.dataquest.io/blog/tutorial-getting-started-with-r-and-rstudio/#tve-jump-173bb264c2b)
Packages into Memory#data science tutorials #beginner #r tutorial #r tutorials #rstats #tutorial #tutorials
1596513720
What exactly is clean data? Clean data is accurate, complete, and in a format that is ready to analyze. Characteristics of clean data include data that are:
Common symptoms of messy data include data that contain:
In this blog post, we will work with five property-sales datasets that are publicly available on the New York City Department of Finance Rolling Sales Data website. We encourage you to download the datasets and follow along! Each file contains one year of real estate sales data for one of New York City’s five boroughs. We will work with the following Microsoft Excel files:
As we work through this blog post, imagine that you are helping a friend launch their home-inspection business in New York City. You offer to help them by analyzing the data to better understand the real-estate market. But you realize that before you can analyze the data in R, you will need to diagnose and clean it first. And before you can diagnose the data, you will need to load it into R!
Benefits of using tidyverse tools are often evident in the data-loading process. In many cases, the tidyverse package readxl
will clean some data for you as Microsoft Excel data is loaded into R. If you are working with CSV data, the tidyverse readr
package function read_csv()
is the function to use (we’ll cover that later).
Let’s look at an example. Here’s how the Excel file for the Brooklyn borough looks:
The Brooklyn Excel file
Now let’s load the Brooklyn dataset into R from an Excel file. We’ll use the readxl
package. We specify the function argument skip = 4
because the row that we want to use as the header (i.e. column names) is actually row 5. We can ignore the first four rows entirely and load the data into R beginning at row 5. Here’s the code:
library(readxl) # Load Excel files
brooklyn <- read_excel("rollingsales_brooklyn.xls", skip = 4)
Note we saved this dataset with the variable name brooklyn
for future use.
The tidyverse offers a user-friendly way to view this data with the glimpse()
function that is part of the tibble
package. To use this package, we will need to load it for use in our current session. But rather than loading this package alone, we can load many of the tidyverse packages at one time. If you do not have the tidyverse collection of packages, install it on your machine using the following command in your R or R Studio session:
install.packages("tidyverse")
Once the package is installed, load it to memory:
library(tidyverse)
Now that tidyverse
is loaded into memory, take a “glimpse” of the Brooklyn dataset:
glimpse(brooklyn)
## Observations: 20,185
## Variables: 21
## $ BOROUGH <chr> "3", "3", "3", "3", "3", "3", "…
## $ NEIGHBORHOOD <chr> "BATH BEACH", "BATH BEACH", "BA…
## $ `BUILDING CLASS CATEGORY` <chr> "01 ONE FAMILY DWELLINGS", "01 …
## $ `TAX CLASS AT PRESENT` <chr> "1", "1", "1", "1", "1", "1", "…
## $ BLOCK <dbl> 6359, 6360, 6364, 6367, 6371, 6…
## $ LOT <dbl> 70, 48, 74, 24, 19, 32, 65, 20,…
## $ `EASE-MENT` <lgl> NA, NA, NA, NA, NA, NA, NA, NA,…
## $ `BUILDING CLASS AT PRESENT` <chr> "S1", "A5", "A5", "A9", "A9", "…
## $ ADDRESS <chr> "8684 15TH AVENUE", "14 BAY 10T…
## $ `APARTMENT NUMBER` <chr> NA, NA, NA, NA, NA, NA, NA, NA,…
## $ `ZIP CODE` <dbl> 11228, 11228, 11214, 11214, 112…
## $ `RESIDENTIAL UNITS` <dbl> 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1…
## $ `COMMERCIAL UNITS` <dbl> 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0…
## $ `TOTAL UNITS` <dbl> 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1…
## $ `LAND SQUARE FEET` <dbl> 1933, 2513, 2492, 1571, 2320, 3…
## $ `GROSS SQUARE FEET` <dbl> 4080, 1428, 972, 1456, 1566, 22…
## $ `YEAR BUILT` <dbl> 1930, 1930, 1950, 1935, 1930, 1…
## $ `TAX CLASS AT TIME OF SALE` <chr> "1", "1", "1", "1", "1", "1", "…
## $ `BUILDING CLASS AT TIME OF SALE` <chr> "S1", "A5", "A5", "A9", "A9", "…
## $ `SALE PRICE` <dbl> 1300000, 849000, 0, 830000, 0, …
## $ `SALE DATE` <dttm> 2020-04-28, 2020-03-18, 2019-0…
The glimpse()
function provides a user-friendly way to view the column names and data types for all columns, or variables, in the data frame. With this function, we are also able to view the first few observations in the data frame. This data frame has 20,185 observations, or property sales records. And there are 21 variables, or columns.
#data science tutorials #beginner #r #r tutorial #r tutorials #rstats #tidyverse #tutorial #tutorials
1594399440
In this blog post, we’ll look at how to use R Markdown. By the end, you’ll have the skills you need to produce a document or presentation using R Mardown, from scratch!
We’ll show you how to convert the default R Markdown document into a useful reference guide of your own. We encourage you to follow along by building out your own R Markdown guide, but if you prefer to just read along, that works, too!
R Markdown is an open-source tool for producing reproducible reports in R. It enables you to keep all of your code, results, plots, and writing in one place. R Markdown is particularly useful when you are producing a document for an audience that is interested in the results from your analysis, but not your code.
R Markdown is powerful because it can be used for data analysis and data science, collaborating with others, and communicating results to decision makers. With R Markdown, you have the option to export your work to numerous formats including PDF, Microsoft Word, a slideshow, or an HTML document for use in a website.
Turn your data analysis into pretty documents with R Markdown.
We’ll use the RStudio integrated development environment (IDE) to produce our R Markdown reference guide. If you’d like to learn more about RStudio, check out our list of 23 awesome RStudio tips and tricks!
Here at Dataquest, we love using R Markdown for coding in R and authoring content. In fact, we wrote this blog post in R Markdown! Also, learners on the Dataquest platform use R Markdown for completing their R projects.
We included fully-reproducible code examples in this blog post. When you’ve mastered the content in this post, check out our other blog post on R Markdown tips, tricks, and shortcuts.
Okay, let’s get started with building our very own R Markdown reference document!
R Markdown is a free, open source tool that is installed like any other R package. Use the following command to install R Markdown:
install.packages("rmarkdown")
Now that R Markdown is installed, open a new R Markdown file in RStudio by navigating to File > New File > R Markdown…
. R Markdown files have the file extension “.Rmd”.
When you open a new R Markdown file in RStudio, a pop-up window appears that prompts you to select output format to use for the document.
The default output format is HTML. With HTML, you can easily view it in a web browser.
We recommend selecting the default HTML setting for now — it can save you time! Why? Because compiling an HTML document is generally faster than generating a PDF or other format. When you near a finished product, you change the output to the format of your choosing and then make the final touches.
One final thing to note is that the title you give your document in the pop-up above is not the file name! Navigate to File > Save As..
to name, and save, the document.
#data science tutorials #beginner #r #r markdown #r tutorial #r tutorials #rstats #rstudio #tutorial #tutorials