---
title: "Introduction to amapro"
date: "`r Sys.Date()`"
output: rmarkdown::html_vignette
description: >
  Start here if this is your first time using amapro. You'll also find information about JavaScript libraries AMap and Loca.
vignette: >
  %\VignetteIndexEntry{Introduction to amapro}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r, echo = FALSE, message = FALSE}
knitr::opts_chunk$set(collapse = TRUE, comment = "#>")
```

Welcoming JavaScript library AMap into the world of R.  
AMap is an advanced mapping library made in China and widely used there. It features 2D/3D animation, supports a multitude of layers and markers, data import, flyover playback, etc. <br>
Library _amapro_ let you control AMap from R and Shiny. It uses AMap's native commands/parameters wrapped in just a few commands.

# Translation

AMap's documentation is in Chinese and most links here make reference to it. If you happen _not_ to know Chinese, it is convenient to set your browser to [auto-translate](https://www.howtogeek.com/407924/how-to-turn-translation-on-or-off-in-chrome/). This will help a little or a lot depending on the website/page structure. One can also copy/paste text to [Google translate](https://translate.google.com?sl=auto&tl=en).
  
# Installation

Install **amapro** from Github with  
``` remotes::install_github("helgasoft/amapro") ```  
CRAN version also available but usually outdated.  

Run with the following commands     <br> 
``` library(amapro); am.init() ``` <br>
A pop-up dialog will ask for an **API key** (shows once, will not be repeated).  <br>
API key is obtained through [registration](https://console.amap.com/dev/id/phone), expecting you to provide a Chinese phone number for SMS verification.  <br>
How to get an API key if you reside out of China? 

- ask a friend from China to help, or hire a local [freelancer](https://www.truelancer.com/freelancers-in-china)
- search the web for a shared key
- use a temporary Chinese phone number from sites like _sms24.me_, _turtle-sms.xyz_,  etc. However most are probably blacklisted as the registration page shows them as _'already registered'_.
- select temporarily the 'demo' option, without guarantee to work in the long run
  
# Shiny Demo

Interactive, hands-on showcase of many library features.
Activate with the following command: <br/>
``` library(amapro); demo(am.shiny) ```


# API links

_amapro_ is based on version 2.0 of AMap (JSAPI v2.0). "API" auto-translates as "Reference book" in web menus.

## AMap
The base library with optional plugins. Most important links are  

* [Summary](https://lbs.amap.com/api/jsapi-v2/summary/)
* [Guide](https://lbs.amap.com/api/jsapi-v2/guide/abc/quickstart)
* [API](https://a.amap.com/jsapi/static/doc/index.html) documentation, good auto-translation
* [Examples](https://lbs.amap.com/demo/list/jsapi-v2) - live demos

## LOCA
AMap extension with enhanced 3D features. In _amapro_ it is invoked with a parameter -  ```am.init(loca=TRUE, ...)```. The documentation auto-translates well in the browser.

* [Intro](https://lbs.amap.com/api/loca-v2/intro)
* [API](https://a.amap.com/Loca/static/loca-v2/doc/html/index.html) documentation

# Commands

Controlling map and elements is done by sending AMap commands to them. Commands can be chained with the pipe operator |&gt; or %&gt;% and are executed sequentially in the order received. <br>
Example: ``` am.cmd('setAngle', 'carIcon', -90) ``` <br>
_amapro_ uses native AMap commands and introduces these <ins>additional</ins>:

* **set** - create new element
    - with _name_: add new global JS object outside the map <br>
    ``` am.cmd('set', 'VectorLayer', name='e$layer1') ```
    - without _name_:  add new element to map  <br>
    ``` am.cmd('set', 'e$marker1', position= c(116.478, 39.998)) ```
* **addTo** - append one existing JS object to another by name  <br>
  ``` am.cmd('addTo', 'e$layer1', 'e$marker1') ```
* **var** - set a JavaScript variable   <br>
  ``` am.cmd('var', 'e$myOpacity', 0.8) ```
* **code** - execute JavaScript code    <br>
  ``` am.cmd('code', 'alert("I am JS");') ```

AMap commands starting with **get** return data from the map or related objects. <br>
Put the data in a Shiny input variable by setting its name in parameter **r**. <br>
Example: ``` am.cmd('getCenter', 'map', r='inShiny1') ``` <br>
Above command will update _input$inShiny1_ with the Lng/Lat coordinates of the map center.

# Events

Events could be defined for map and elements. All types of instances use **on/off methods** to bind and remove events. <br>
Events are set in attribute **on**(or **off**) as a list of lists. Each event is a separate list with event name in **e**, a JS function **f** and optionally a query **q**.  
Example: 
```r
am.init(center= c(116.475, 39.997), zoom= 17,
        on= list(list(e= 'complete', 
                      f= "function() {alert('loaded!');}")) )
```
on/off events without _name_ are ignored, except for the map itself (as above example).  <br>
JavaScript function _Shiny.setInputValue()_ can be used to send data back to Shiny.

# Limitations

- only one map is created by _am.init_ per session. It is a JS global called 'm$jmap'.
- AMap command [addTo](https://a.amap.com/jsapi/static/doc/index.html#controladdto) is overwritten by _amapro_ and cannot be used.
- the **supported AMap plugins** are: ControlBar, Scale, ToolBar, MoveAnimation, MouseTool, HeatMap, GeoJSON, ElasticMarker.
- most **built-in** AMap tile layers (Satellite, Traffic, Roads) are limited to China only. However, with command _am.item('TileLayer')_, one can use any [Leaflet provider](https://leaflet-extras.github.io/leaflet-providers/preview/) for worldwide coverage.
- AMap built-in [map layers](https://lbs.amap.com/api/jsapi-v2/guide/layers/official-layers) are [GCJ-02 coded](https://en.wikipedia.org/wiki/Restrictions_on_geographic_data_in_China) and coordinates collected on them will display incorrectly in Leaflet or other WGS-84 based maps, and vice-versa. They need to be [converted](https://lbs.amap.com/api/jsapi-v2/guide/transform/convertfrom). Conversion is available through function [convertFrom](https://lbs.amap.com/api/jsapi-v2/documentation#convertfrom).
- AMap ecosystem is vast, **unsupported features** include:
  'BesizerCurve', 'MarkerCluster', 'HawkEye',   [IndoorMap](https://lbs.amap.com/demo/javascript-api/example/indoormap/indoormap/), 
    [CustomLayer](https://lbs.amap.com/demo/javascript-api/example/selflayer/cus-svg),  'GLCustomLayer', 'DistrictLayer', 'LayerGroup',
 all editors like 'PolygonEditor','Webservice', 'Search(AMap.Autocomplete, AMap.PlaceSearch)', 'Geocoding(AMap.Geocoder)', Route planning, other services(weather, districts, etc.), positioning, utilities.
- most **Loca** elements are supported, but not all have been tested. Latest _AmbientLight_, _DirectionalLight_ and _PointLight_ objects are not supported, but parameters _ambLight_, _dirLight_ and _pointLight_ accomplish the same. Loca events are not supported yet.
- _loca.js_ file has several versions, the latest (bigger) one does not work well with the current _amap.js_ 

	
# Tips

- all named objects created in JS are [global variables](https://developer.mozilla.org/en-US/docs/Glossary/Global_object) (_window.name_). Good practice is to use a name prefix (m$) to avoid overwriting accidentally external variables.

- API attributes could be set to a JS function instead of a value. Function is defined as a string starting with word "function".

- usually WMS/WMTS tiles come from external servers and may present a CORS problem - browser refusal to load. One can install a small [extension in  Chrome](https://chrome.google.com/webstore/detail/allow-cors-access-control/lhobafahddgcelffkeicbaginigeejlf) or [Firefox](https://addons.mozilla.org/en-US/firefox/addon/access-control-allow-origin/) to fix this problem manually inside the browser.

- AMap has several predefined [Map styles](https://lbs.amap.com/api/jsapi-v2/guide/map/map-style/). Could be set in map options with _mapStyle_.

- _amapro_ silent errors are collected in the browser Console. Press key **F12** to open the dev.environment, then open tab "Console" to view them.

- Chrome/Firefox extensions may interfere with map presentation (like 'uBlock')
  
  
