Question

I’m trying to read data into my calendar visualisation using JSON. At
the moment it works great using a CSV file:

d3.csv("RSAtest.csv", function(csv) {
  var data = d3.nest()
    .key(function(d) { return d.date; })
    .rollup(function(d) { return d[0].total; })
    .map(csv);

 rect.filter(function(d) { return d in data; })
      .attr("class", function(d) { return "day q" + color(data[d]) +
"-9"; })
      .select("title")
      .text(function(d) { return d + ": " + data[d]; });

});

It reads the following CSV data:

date,total
2000-01-01,11
2000-01-02,13
.
.
.etc

Any pointers on how I can read the following JSON data instead:
{"2000-01-01":19,"2000-01-02":11......etc}

I tried the following but it not working for me (datareadCal.php spits
out the JSON for me):

d3.json("datareadCal.php", function(json) {
  var data = d3.nest()
    .key(function(d) { return d.Key; })
    .rollup(function(d) { return d[0].Value; })
    .map(json); 

thanks

Answer 1

You can use d3.entries() to turn an object literal into an array of key/value pairs:

var countsByDate = {'2000-01-01': 10, ...};
var dateCounts = d3.entries(countsByDate);
console.log(JSON.stringify(dateCounts[0])); // {"key": "2000-01-01", "value": 10}

One thing you’ll notice, though, is that the resulting array isn’t properly sorted. You can sort them by key ascending like so:

dateCounts = dateCounts.sort(function(a, b) {
    return d3.ascending(a.key, b.key);
});