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chart_segment.js
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chart_segment.js
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const DEBUG = require('./debug.js');
const Utils = require('./utils.js');
class ChartSegment {
constructor(buffer, fastName, slowName) {
this.buffer = buffer;
this.fast = this.buffer.map(function(el) {
return el.indicators[fastName];
});
this.slow = this.buffer.map(function(el) {
return el.indicators[slowName];
});
this.shapeHash = null;
}
/**
* Calculates the shapehash of a given segment of chart
* @param {*} numberOfDivisions specifies the number of divisions/strips we want for the hash, number of segments equates to half the hash length
* @throws Throws an error if there is an issue with the inputted buffer
*/
calculateShapeHash(numberOfDivisions) {
//Perform checks before calculating shape hash
if (this.shapeHash != null) {
return this.shapeHash;
}
if (!(this.buffer.length % (numberOfDivisions - 1) == 0)) {
throw new Error(`The buffer length of ${this.buffer.length} is not divisible by the numberOfDivisions (${numberOfDivisions}).`)
}
if (this.fast.length != this.slow.length) {
throw new Error(`The fast and slow arrays are of different lengths: ${this.fast.length} and ${this.slow.length}.`);
}
let lowestPoint = Infinity;
for (let i = 0; i < this.fast.length; i ++) {
let currentFast = this.fast[i];
let currentSlow = this.slow[i];
// DEBUG.log("EMAS", currentFast, currentSlow);
if (currentFast < lowestPoint) {
lowestPoint = currentFast;
}
if (currentSlow < lowestPoint) {
lowestPoint = currentSlow;
}
}
let hash = "";
let divisionSpacing = this.buffer.length / (numberOfDivisions - 1);
for (let i = 0; i <= this.buffer.length; i += divisionSpacing) {
if (i == this.buffer.length) {
i -= 1;
}
let fast = this.fast[i];
let slow = this.slow[i];
let slowPd = Utils.percentageChange(slow, lowestPoint);
let fastPd = Utils.percentageChange(fast, lowestPoint);
let slowChar = this.getLetterFromPercentage(slowPd);
let fastChar = this.getLetterFromPercentage(fastPd);
hash += `${slowChar}${fastChar}`;
}
return hash;
}
getLetterFromPercentage(percentage) {
let letters = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'];
let trimmed = Number(percentage.toFixed(2));
let total = 0;
for (let i = 0; i < letters.length; i++) {
let currentLetter = letters[i];
total += 0.01;
total = Number(total.toFixed(2))
if (i == 0 && trimmed < total) {
return 'A';
} else if (i == letters.length - 1 && trimmed > total) {
return 'Z';
}
if (trimmed == total) {
return currentLetter;
}
}
}
}
module.exports = ChartSegment;