Using d3.js to dynamically change the color of svg elements based on their data values

Question

Using d3.js to dynamically change the color of svg elements based on their data values

I was searching for a way to dynamically color SVG rectangles based on values from a dataset. If I were to create rectangles for each data entry, how could I adjust the rectangle's color according to the data value?

Here is what I currently have:

//Create an SVG Container
var svgContainer = d3.select("body").selectAll("svg")
                     .data(data)
                     .enter().append("svg")
                     .attr("width", 38)
                     .attr("height", 25);

//Draw the rectangle
var rectangle = svgContainer.append("rect")
                    .attr("x", 5)
                    .attr("y", 5)
                    .attr("width", 38)
                    .attr("height", 25)
                    //Adjusting color here based on data points; aiming for different shades of red based on data values
                    .style("fill", function(d) {
                        return "rgb(255," + (d.Two * 2) + ",0)";
                    });

Assuming my data appears as follows:

var data = [{One:420, Two:222, Three:332},...]; And I desire only the "Two" values to influence the color of the rectangles

javascript html css d3.js svg

Answer 1

Answer №1

If you need to implement specific color codes, the following example will provide guidance.

The d3 color scale d3.scale.category10() contains 20 colors
Create a selection of colors to use within your code
Assign colors based on the value

var rectangle = svgContainer.selectAll("rect")
                .data(data).enter()
            .append("rect")
            .attr("x", function(d,i){ return 40*i})
            .attr("y", 5)
            .attr("width", 38)
            .attr("height", 25)
           .style("fill", function(d){ return d.Two <= 222 ? 'red' : 'green' });

View Live Demo

Answer 2

If you need to implement specific color codes, the following example will provide guidance.

The d3 color scale d3.scale.category10() contains 20 colors
Create a selection of colors to use within your code
Assign colors based on the value

var rectangle = svgContainer.selectAll("rect")
                .data(data).enter()
            .append("rect")
            .attr("x", function(d,i){ return 40*i})
            .attr("y", 5)
            .attr("width", 38)
            .attr("height", 25)
           .style("fill", function(d){ return d.Two <= 222 ? 'red' : 'green' });

View Live Demo

Answer 3

Answer №2

This code snippet contains an error:

    var svgContainer = d3.select("body").selectAll("svg")
                             .data(data)//INCORRECT
                             .enter().append("svg")
                             .attr("width", 38)
                             .attr("height", 25);

The mistake here is that it creates multiple SVG elements based on the dataset.

A corrected version would be:

 var svgContainer = d3.select("body")
   .append("svg")
   .attr("width", 38)
   .attr("height", 25);

To add color to rectangles:

//create a color scale
         var c10 = d3.scale.category10();

Now, create one rectangle per data point from the dataset

     //Draw the rectangle
     var rectangle = svgContainer.selectAll("rect").data(data).enter().append("rect")
       .attr("x", 5)
       .attr("y", 5)
       .attr("width", 38)
       .attr("height", 25)
       //coloring the rectangles based on data values, varying shades of red
       .style("fill", function(d){ return c10(d.One)});//using the color scale.

Here is a link to a working example

Answer 4

This code snippet contains an error:

    var svgContainer = d3.select("body").selectAll("svg")
                             .data(data)//INCORRECT
                             .enter().append("svg")
                             .attr("width", 38)
                             .attr("height", 25);

The mistake here is that it creates multiple SVG elements based on the dataset.

A corrected version would be:

 var svgContainer = d3.select("body")
   .append("svg")
   .attr("width", 38)
   .attr("height", 25);

To add color to rectangles:

//create a color scale
         var c10 = d3.scale.category10();

Now, create one rectangle per data point from the dataset

     //Draw the rectangle
     var rectangle = svgContainer.selectAll("rect").data(data).enter().append("rect")
       .attr("x", 5)
       .attr("y", 5)
       .attr("width", 38)
       .attr("height", 25)
       //coloring the rectangles based on data values, varying shades of red
       .style("fill", function(d){ return c10(d.One)});//using the color scale.

Here is a link to a working example

Using d3.js to dynamically change the color of svg elements based on their data values

Answer №1

Answer №2

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