Determining the decimal power using the position of a for-loop

Question

Determining the decimal power using the position of a for-loop

After selecting a number, the task is to generate circles using d3.js. Each circle will be assigned a color from an array:

var color =["red", "blue", "yellow", "orange",.....]

● For instance, if the user picks 593, the first 500 circles should be red (color[0]), the next 90 blue (color[1]), and the last 3 yellow (color[2]) because

593 = 500 + 90 + 3 = 5 * 10^2 + 9 * 10^1 + 3 * 10^0

or with

var number = 593
var number_as_array = number.toString().split('');

Hence,

593 = 5 * number_as_array[0] * 10^(number_as_array.length - 1) + 9 * number_as_array[1] * 10^(number_as_array.length - 2) + 3 * number_as_array[2] * 10^(number_as_array.length - 3)

● If the chosen number is 4168, then 4000 circles will be red, the following 100 blue, another 60 yellow, and the remaining 8 orange.

To set the color for each circle, an array of JS objects is created using a for loop:

var data=[]
for (index = 0; index < number; index++){
circle= {};
        circle.cx = circle_x;
        circle.cy = circle_y;
        circle.color = color[????]
        data.push(circle);

The challenge lies in how to assign colors to circle.color based on the mentioned criteria?

javascript arrays for-loop d3.js decimal

Answer 1

Answer №1

Not to take away from the previous response, here is another way to approach the problem.

Given a total number of circles, this method determines how many significant digits of the total are needed (rounding down) so that any given index is less than the rounded total.

If we have 132 circles in total:

Indexes 0 through 99 will be less than 100 (132 rounded down with one significant digit).
Indexes 100 through 129 will be less than 130 (132 rounded down with two significant digits).
Indexes 130 and 131 will be less than 132 (132 with all significant digits).

Here's a visual representation (each row represents 50 circles):

var svg = d3.select("body")
  .append("svg")
  .attr("width",510)
  .attr("height",510);
  
var n = 377;

var color = d3.scaleOrdinal()
.range(["steelblue","orange","crimson","lawngreen","pink"])

var digits = Math.floor(Math.log10(n));

var circles = svg.selectAll("circle")
  .data(d3.range(n))
  .enter()
  .append("circle")
  .attr("cx",function(d,i) { return i%50 * 10 + 5 })
  .attr("cy",function(d,i) { return Math.floor(i/50) * 10 + 5 })
  .attr("r",5)
  .attr("fill", function(d,i) {
    var exp = digits;
    while (i < Math.floor(n/Math.pow(10,digits-exp))*Math.pow(10,digits-exp)) {
      exp--;
    }
    return color(exp);
  })

<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.10.0/d3.min.js"></script>

Answer 2

Not to take away from the previous response, here is another way to approach the problem.

Given a total number of circles, this method determines how many significant digits of the total are needed (rounding down) so that any given index is less than the rounded total.

If we have 132 circles in total:

Indexes 0 through 99 will be less than 100 (132 rounded down with one significant digit).
Indexes 100 through 129 will be less than 130 (132 rounded down with two significant digits).
Indexes 130 and 131 will be less than 132 (132 with all significant digits).

Here's a visual representation (each row represents 50 circles):

var svg = d3.select("body")
  .append("svg")
  .attr("width",510)
  .attr("height",510);
  
var n = 377;

var color = d3.scaleOrdinal()
.range(["steelblue","orange","crimson","lawngreen","pink"])

var digits = Math.floor(Math.log10(n));

var circles = svg.selectAll("circle")
  .data(d3.range(n))
  .enter()
  .append("circle")
  .attr("cx",function(d,i) { return i%50 * 10 + 5 })
  .attr("cy",function(d,i) { return Math.floor(i/50) * 10 + 5 })
  .attr("r",5)
  .attr("fill", function(d,i) {
    var exp = digits;
    while (i < Math.floor(n/Math.pow(10,digits-exp))*Math.pow(10,digits-exp)) {
      exp--;
    }
    return color(exp);
  })

<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.10.0/d3.min.js"></script>

Answer 3

Answer №2

let colors = ["red","orange", "yellow", "green", "blue", "indigo", "violet"];
let totalCircles = "4192"; // make sure to keep as string
let len = totalCircles.length;
let circleArray = [];
for (let x = 0; x < len; x++) {
    let digitValue = totalCircles.substring(x, x+1);
    let exponentVal = len - x - 1;
    let finalNumber = digitValue * Math.pow(10, exponentVal);
    circleArray.push(finalNumber); // consider using .unshift instead of .push
}
console.log(circleArray);
for (let y = 0; y < circleArray.length; y++) {
    for (let z = 0; z < circleArray[y]; z++) {
        drawCircle(colors[y]);
    }
}

Answer 4

let colors = ["red","orange", "yellow", "green", "blue", "indigo", "violet"];
let totalCircles = "4192"; // make sure to keep as string
let len = totalCircles.length;
let circleArray = [];
for (let x = 0; x < len; x++) {
    let digitValue = totalCircles.substring(x, x+1);
    let exponentVal = len - x - 1;
    let finalNumber = digitValue * Math.pow(10, exponentVal);
    circleArray.push(finalNumber); // consider using .unshift instead of .push
}
console.log(circleArray);
for (let y = 0; y < circleArray.length; y++) {
    for (let z = 0; z < circleArray[y]; z++) {
        drawCircle(colors[y]);
    }
}

Answer 5

Answer №3

If you're looking for an ideal scenario to utilize D3's Threshold Scales, this is it: input N numbers to indicate color breaks, and receive N+1 colors back for any given value. Take a look at this example straight from the documentation:

var color = d3.scaleThreshold()
    .domain([0, 1])
    .range(["red", "white", "green"]);

color(-1);   // "red"
color(0);    // "white"
color(0.5);  // "white"
color(1);    // "green"
color(1000); // "green"

In your case, the task is figuring out how to transform your input (e.g., 593) into the array of two numbers [500, 590]:

var sinput = 593 + ""; // convert input to string
var digits = sinput.split("").slice(0, -1); // utilize all digits except the last one
var breaks = digits.map((d, i, a) =>
    +(a.slice(0, i+1).join("")) * Math.pow(10, a.length-i)
);

var colors = ["red", "blue", "yellow", "orange"];
var tScale = d3.scaleThreshold()
    .domain(breaks)
    .range(colors);

Values less than 500 are labeled "red," those between 500 and 589 are "blue," and anything greater than or equal to 590 becomes "yellow." The fourth color in the range ("orange") remains unused unless handling a four-digit number as input.

Note: This method assumes the input will be at least two digits long.

Now, instead of pre-defining colors in the data array, you can dynamically assign them during circle creation with code like

.attr("color", (d, i) => tScale(i))

Answer 6

If you're looking for an ideal scenario to utilize D3's Threshold Scales, this is it: input N numbers to indicate color breaks, and receive N+1 colors back for any given value. Take a look at this example straight from the documentation:

var color = d3.scaleThreshold()
    .domain([0, 1])
    .range(["red", "white", "green"]);

color(-1);   // "red"
color(0);    // "white"
color(0.5);  // "white"
color(1);    // "green"
color(1000); // "green"

In your case, the task is figuring out how to transform your input (e.g., 593) into the array of two numbers [500, 590]:

var sinput = 593 + ""; // convert input to string
var digits = sinput.split("").slice(0, -1); // utilize all digits except the last one
var breaks = digits.map((d, i, a) =>
    +(a.slice(0, i+1).join("")) * Math.pow(10, a.length-i)
);

var colors = ["red", "blue", "yellow", "orange"];
var tScale = d3.scaleThreshold()
    .domain(breaks)
    .range(colors);

Values less than 500 are labeled "red," those between 500 and 589 are "blue," and anything greater than or equal to 590 becomes "yellow." The fourth color in the range ("orange") remains unused unless handling a four-digit number as input.

Note: This method assumes the input will be at least two digits long.

Now, instead of pre-defining colors in the data array, you can dynamically assign them during circle creation with code like

.attr("color", (d, i) => tScale(i))

Answer 7

Answer №4

The proposed solutions appear to be excessively intricate. One method involves breaking down the number into individual digits and then creating 10^digitIndex circles with colors corresponding to the index of each digit. A precautionary line has been included to ensure that the number is not too large.

function mapColors(num) {
  var color =['red','blue', 'yellow', 'orange'];
  
  // Check if the number exceeds the length of the color array
  if ((''+num).length > color.length) return;
  
  return (''+num).split('').reduce(function (acc, n, i, arr) {
    for (var j=n*Math.pow(10, arr.length-i-1); j; --j) {
      acc.push({'color':color[i]});
      // Add additional circle properties here
    }
    return acc;
  }, []);
}

console.log(mapColors(23));

Answer 8

The proposed solutions appear to be excessively intricate. One method involves breaking down the number into individual digits and then creating 10^digitIndex circles with colors corresponding to the index of each digit. A precautionary line has been included to ensure that the number is not too large.

function mapColors(num) {
  var color =['red','blue', 'yellow', 'orange'];
  
  // Check if the number exceeds the length of the color array
  if ((''+num).length > color.length) return;
  
  return (''+num).split('').reduce(function (acc, n, i, arr) {
    for (var j=n*Math.pow(10, arr.length-i-1); j; --j) {
      acc.push({'color':color[i]});
      // Add additional circle properties here
    }
    return acc;
  }, []);
}

console.log(mapColors(23));

Determining the decimal power using the position of a for-loop

Answer №1

Answer №2

Answer №3

Answer №4

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