ASCII frequency graph

frequency.js

//sample data

let yAxis = [5,15]
let xAxis = [140, 190]
let dataSet = [
  [140,150,15],
  [160,170,10],
  [170,180,8],
  [180,190,5],
]

let yValues = range(yAxis)
let xValues = range([xAxis[0], xAxis[1], dataSet[0][1]-dataSet[0][0]]);

//return an array with values of a given range
// [1,8] -> [1,2,3...,8]
function range([start, end, inc=1]){
  
  let rangeCollector = []
  for(let i = start; i<=end; i=i+inc){
    rangeCollector.push(i)
  }
  return rangeCollector;
}

// draw y axis values considering padding 
function drawYAxis(yValues){
  //in the case:
  //100
  // 99
  //get max value
  let maxValue = yValues[yValues.length - 1]
  //convert all integers to string
  let yValuesAligned = yValues.map(n=>{
    return numberToAlignedString(n,(maxValue).toString().length)
  })
  return yValuesAligned;
}

// @return string
// draw x axis values
function drawXAxis(xValues, mark=" "){
  let xValuesSpaced = xValues.reduce((acc,v)=>{
    acc = acc.toString()+mark+ v.toString()
    return acc;
  }, "")
  return xValuesSpaced;
}
// draw the point mark for a given interval [start, end]
// @return string with just the mark at the right position
function drawXPoint(xValues, start, end, point="*"){
  //mark the point in the xAxis when the value is between start-end
  let xValuesSpaced = xValues.reduce((acc,v)=>{
    let mark = ""
    if(v > start && v <= end){
      mark = point;
    }
    acc = acc.toString()+mark+ convertNumberToSpaces(v).toString()
    return acc;
  }, "")
  return xValuesSpaced;
}

//add leading spaces to number
function numberToAlignedString(number, maxSeparation=0, spaceMark=" "){
  while(number.toString().length < maxSeparation){
    number = " " + number
  }
  return number.toString()
}

// convert number values to white spaces
function convertNumberToSpaces(number){
  
  if(!isNaN(number)){
    
    let s = ""
    for(let i=0; i<=(number).toString().length; i++){
      s = s + " "
    }
    return s
  }
  return number
}

// look up the [x] range for a given y
// @return [start, end]
function findXIntervalForY(dataset, y){
  let pair = []
  dataset.forEach(v=>{
    if(v[2] === parseInt(y)){
      pair = [v[0], v[1]]
    }
  })
  return pair;
}

let y = drawYAxis(yValues)
let x = drawXAxis(xValues)

//draw grid and points
//iterate over all the y values and draw a point from [x,yn] to [x,y0] to 
//represent the frequency of that point

let grid = [];

y.sort((a,b)=>{
  if(a-b < 1) return 1
  if(a==b) return 0
  return -1
}).map(yp=>{
  //draw the point corresponding to the [x,y] coordinate
  let [start, end] = findXIntervalForY(dataSet,yp)
  let xp = drawXPoint(xValues, start, end).split("")
  //to repeat the frequency value for a range not explicitly indicated in the dataset, make sure to merge 
  //the previous line with the new one for the given y point
  merge(grid, xp)
  //print out
  console.log(yp + grid.join(""))
})

function merge(a,b){
  b.forEach((v,k)=>{
    if(a[k]!==undefined && v === "*"){
      a[k] = v
    }else if(a[k] === undefined){
      a.push(v)
    }
  })
  return a
}
//guarantee perfect alignment between the x and y axis
console.log(convertNumberToSpaces(yValues[yValues.length-1])+x)