Introduction
This article demonstrates how to create and use a line chart using vega in reactjs. This article starts with the introduction of the react-vega package. After that, it demonstrates how vega json file works for creating any chart using its json formatted data.
What is Vega?
Vega is a visualization grammar, a declarative language for creating, saving, and sharing interactive visualization designs.With Vega, you can describe the visual appearance and interactive behavior of a visualization in a JSON format, and generate web-based views using Canvas or SVG.
Reference from: Vega
To achieve this feature we will use a npm package npm i react-vega. Using this you can modify the json file and create it according to your requirement.
Prerequisites
- Basic knowledge of ReactJS
- Visual Studio Code
- Node and NPM installed
Step 1. Install NPM dependencies Create a React.js Project
Let's create a new React project by using the following command.
npx create-react-app react-linechart
Step 2. Install NPM dependencies
npm i react-vega
Step 3. Creating a Component
Now go to the src folder and create a new folder and inside in it create a component, 'line-chart.js'. Add the following code to this component.
import React, { useState } from "react";
import { Vega } from 'react-vega';
import "./_linechart.css";
import linecharttimeline from "./linecharttimeline.json";
import linechart180days from "./linechart180days.json";
import linechart30days from "./linechart30days.json";
import linechartLTM from "./linechartLTM.json";
const LineChart = () => {
const [dateFormat, setdateFormat] = useState("%Y");
const [stockPriceData, setstockPriceData] = useState(linecharttimeline);
const stockPrice30Days = linechart30days;
const stockPrice180Days = linechart180days;
const stockPriceLTM = linechartLTM;
const stockPrice=[
{
"name": "source_0",
"values": stockPriceData
},
{
"name": "data_0",
"source": "source_0",
"transform": [
{"type": "formula", "expr": "toDate(datum[\"date\"])", "as": "date"}
]
}
]
const lineSpec ={
"$schema": "https://vega.github.io/schema/vega/v5.json",
"description": "Google's stock price over time.",
"background": "#2e2e38",
"padding": 5,
"width": 700,
"height": 240,
"style": "cell",
"data": stockPrice,
"marks": [
{
"name": "pathgroup",
"type": "group",
"from": {
"facet": {
"name": "faceted_path_main",
"data": "data_0",
"groupby": ["status_mean"]
}
},
"encode": {
"update": {
"width": {"field": {"group": "width"}},
"height": {"field": {"group": "height"}}
}
},
"marks": [
{
"name": "marks",
"type": "line",
"style": ["line"],
"sort": {"field": "datum[\"date\"]"},
"from": {"data": "faceted_path_main"},
"encode": {
"update": {
"tooltip": {"signal": "'Stock Price: '+datum.value+' '+(utcFormat(datum[\"date\"], '%d %b %Y'))"},
"t":"",
"stroke": {"scale": "color", "field": "status_mean"},
"description": {
"signal": "\"date: \" + (utcFormat(datum[\"date\"], '%Y')) + \"; Price(USD): \" + (format(datum[\"value\"], \"\")) + \"; Stock Price: \" + (isValid(datum[\"status_mean\"]) ? datum[\"status_mean\"] : \"\"+datum[\"status_mean\"])"
},
"x": {"scale": "x", "field": "date"},
"y": {"scale": "y", "field": "value"},
"defined": {
"signal": "isValid(datum[\"date\"]) && isFinite(+datum[\"date\"]) && isValid(datum[\"value\"]) && isFinite(+datum[\"value\"])"
}
}
}
}
]
}
],
"scales": [
{
"name": "x",
"type": "utc",
"domain": {"data": "data_0", "field": "date"},
"range": [0, {"signal": "width"}]
},
{
"name": "y",
"type": "linear",
"domain": {"data": "data_0", "field": "value"},
"range": [{"signal": "height"}, 0],
"nice": true,
"zero": false
},
{
"name": "color",
"type": "ordinal",
"domain": {"data": "data_0", "field": "status_mean", "sort": true},
"range": ["#ff736a"]
}
],
"axes": [
{
"scale": "y",
"orient": "left",
"gridScale": "x",
"grid": true,
"tickCount": {"signal": "ceil(height/40)"},
"domain": false,
"labels": false,
"aria": false,
"maxExtent": 0,
"minExtent": 0,
"ticks": false,
"zindex": 0
},
{
"scale": "x",
"orient": "bottom",
"grid": false,
"domain": false,
"format":dateFormat,
"ticks": false,
"labelFlush": true,
"labelOverlap": true,
"tickCount": {"signal": "ceil(width/60)"},
"zindex": 0
},
{
"scale": "y",
"orient": "left",
"grid": false,
"title": "Price(USD)",
"labelOverlap": true,
"tickCount": {"signal": "ceil(height/60)"},
"zindex": 0,
"titleColor":"white"
}
],
"legends": [
{"stroke": "color", "direction": "horizontal","titleOrient":"left","symbolFillColor":"#ff736a","labelColor":"#2e2e38","title":"Stock price","titleColor":"white","labelBaseline":"alphabetic" }
],
"config": {
"axis": {"labelColor": "white","domain": false, "grid": false, "ticks": false},
"legend": {"title": "This is the Title","orient": "bottom", "symbolType": "circle"},
"style": {"cell": {"stroke": null}}
}
}
const onOptionChangeHandler = (event) => {
setdateFormat(getLabelFormat(event.target.value));
}
const getLabelFormat = (chartMode) => {
setstockPriceData([]);
switch (chartMode) {
case "30":
setstockPriceData([...stockPrice30Days]);
return "%m/%d";
case "180":
setstockPriceData([...stockPrice180Days]);
return "%b %Y";
case "LTM":
setstockPriceData([...stockPriceLTM]);
return "%b %Y";
default:
setstockPriceData([...stockPriceData]);
return "%Y";
}
};
return (
<>
<select onChange={onOptionChangeHandler} name="cars" id="cars">
<option value="10Years">10 Years</option>
<option value="30">30 Days</option>
<option value="180">180 Days</option>
<option value="LTM">LTM</option>
</select>
<Vega spec={lineSpec} actions={false}/>
</>
);
};
export default LineChart;
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