How to select unique values in d3.js from data

d3.js, html, javascript

Solution

Filter your data retaining unique keys only by `d3.map`

d3.select("#road").selectAll("option")
    .data(d3.map(data, function(d){return d.roadname;}).keys())
    .enter()
    .append("option")
    .text(function(d){return d;})
    .attr("value",function(d){return d;});

Problem

I am using the following code to populate my Combobox using d3.js ``` d3.csv("Results_New.txt", function(data) { dataset=data; d3.select("#road").selectAll("option") .data(data).enter().append("option").text(function(d){return d.roadname;}).attr("value",function(d){return d.roadname;}); }); ``` There are different rows with the same name. The combobox is populating with these duplicate names. For example in multiple rows the name of the road is I-80.But in the combobox I want to see I-80 only once. How can I do that?

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