Adding Attributes while parsing CSV file in D3

Question

I am trying to parse data in d3 using the csv function. I am attempting to give each datapoint a new attribute (Region) during processing. Outside the CSV function I defined a function that is supposed to take the datapoint, check to see if the state is Alabama, and if so, assign the Region attribute to a string of either "North" or "South".

var parseRegion = (function(d){
        if(d.State === "Alabama"){
        return "South";
       }
      else {
        return "North";
        }
    });

However, when I run the code, every datapoint is assigned a "Region" attribute that is assigned to the function itself. In other words, it is assigned the actual code, rather than the return values. What am I doing wrong??

d3.csv("data.csv").get(function(error,data){
if (error) throw error;

data.forEach(function(d){
   d.Deaths = +d.Deaths;
   d.Population = +d.Population;
   d.Year = parseDate(d.Year);
   d.Region = parseRegion;
});

Thanks for any help you can provide. Eventually I will add additional states besides Alabama of course.

RobinL · Accepted Answer · 2017-06-10 16:22:51Z

2

Your problem is that you're not calling the parseRegion function that you define.

So you need

 d.Region = parseRegion(d);

More generally d3.csv provides a way to parse the data without the use of forEach. You can do the following:

d3.csv("data.csv")
    .row(function(d) {
    //Code to parse data row by row goes here
    })
    .get(function(error,data){
    //Data is now the whole parsed dataset
    });

answered Jun 10, 2017 at 16:22

RobinL

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1 Comment

Harrison Cramer Over a year ago

Thank you. This worked perfectly, and thanks for the clarification on the .row function.

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