D3JS makes date duplicates - d3.js

Question

I have this d3js code:
var tooltip = tooltipd3();
var svg = d3.select("svg#svg-day"),
margin = {
top: 20,
right: 30,
bottom: 30,
left: 25,
padding: 15
},
width = 700 - margin.left - margin.right,
height = 300 - margin.top - margin.bottom;
// parse the periodo / time
var parseTime = d3.timeParse("%Y-%m-%d");
// set the ranges
var x = d3.scaleTime().range([0, width - margin.padding]);
var y = d3.scaleLinear().range([height, 0]);
// define the area
var area = d3.area()
.x(function(d) {
return x(d.periodo) + (margin.left + margin.padding);
})
.y0(height)
.y1(function(d) {
return y(d.guadagno);
});
// define the line
var valueline = d3.line()
.x(function(d) {
return x(d.periodo) + (margin.left + margin.padding);
})
.y(function(d) {
return y(d.guadagno);
});
var div = d3.select("svg#svg-day")
.append("div") // declare the tooltip div
.attr("class", "tooltip") // apply the 'tooltip' class
.style("opacity", 0);
// get the data
d3.csv(base_url() + 'graph/getStatementsDaily/', function(error, data) {
if (error) throw error;
$('.graph-loading').hide();
// format the data
data.forEach(function(d) {
d.periodo = parseTime(d.periodo)
d.guadagno = +d.guadagno;
});
// scale the range of the data
x.domain(d3.extent(data, function(d) {
return d.periodo;
}));
y.domain([0, d3.max(data, function(d) {
return d.guadagno + ((d.guadagno / 100) * 10); // 10% in più sulla scala numerica
})]);
// add the area
svg.append("path")
.data([data])
.attr("class", "area")
.attr("d", area);
// add the valueline path.
svg.append("path")
.data([data])
.attr("class", "line")
.attr("d", valueline);
// Add the scatterplot
svg.selectAll("dot")
.data(data)
.enter().append("circle")
.attr("class", "dot")
.attr("r", 3)
.attr("cx", function(d) {
return x(d.periodo) + (margin.left + margin.padding);
})
.attr("cy", function(d) {
return y(d.guadagno);
})
.on('mouseover', function(d) {
var html = '<h5>' + d.guadagno + ' €</h5>';
tooltip.mouseover(html); // pass html content
})
.on('mousemove', tooltip.mousemove)
.on('mouseout', tooltip.mouseout);
// add the X Axis
svg.append("g")
.attr("class", "x axis")
.attr("transform", "translate(" + (margin.left + margin.padding) + "," + (height) + ")")
//HERE IS THE DATES CODE
.call(d3.axisBottom(x).tickFormat(d3.timeFormat("%d/%m")))
// add the Y Axis
svg.append("g")
.attr("class", "y axis")
.attr("transform", "translate (" + (margin.left + margin.padding) + " 0)")
.call(d3.axisLeft(y));
});
The dates care coming from a CSV file that has this format:
periodo,guadagno
2017-05-08,0.0
2017-05-09,0.5385
2017-05-10,0.0
2017-05-11,0.0
2017-05-12,0.0
2017-05-13,0.5680
2017-05-14,0.0
2017-05-15,0.0
The result is fine with lots of dates, but with 7 dates I get duplicates as you can see here:
Why is this?? And how do I fix it?

Answer 1

This is something that bothers a lot of people new to D3: the ticks in the axis, specially when using a time scale, are automatically generated. In your case, given the date interval in your domain, it coincidentally ended up creating two ticks for each day. But pay attention to this: those ticks represent different times (hours) in the same day (you can see that if you remove the tickFormat in the axis generator).
Let's see your code generating the x axis:
var svg = d3.select("svg");
var data = d3.csvParse(d3.select("#csv").text());
var parseTime = d3.timeParse("%Y-%m-%d");
data.forEach(function(d) {
d.periodo = parseTime(d.periodo)
});
var x = d3.scaleTime()
.range([20, 480])
.domain(d3.extent(data, function(d) {
return d.periodo;
}));
var axis = d3.axisBottom(x).tickFormat(d3.timeFormat("%d/%m"))(svg.append("g").attr("transform", "translate(0,50)"));
pre {
display: none;
}
<script src="https://d3js.org/d3.v4.min.js"></script>
<svg width="500"></svg>
<pre id="csv">periodo,guadagno
2017-05-08,0.0
2017-05-09,0.5385
2017-05-10,0.0
2017-05-11,0.0
2017-05-12,0.0
2017-05-13,0.5680
2017-05-14,0.0
2017-05-15,0.0</pre>
As you can see, there are two ticks for each day (remember, for different hours).
Let's show that this is a coincidence: This is the same code, but changing the last date for 2017-05-20:
var svg = d3.select("svg");
var data = d3.csvParse(d3.select("#csv").text());
var parseTime = d3.timeParse("%Y-%m-%d");
data.forEach(function(d) {
d.periodo = parseTime(d.periodo)
});
var x = d3.scaleTime()
.range([20, 480])
.domain(d3.extent(data, function(d) {
return d.periodo;
}));
var axis = d3.axisBottom(x).tickFormat(d3.timeFormat("%d/%m"))(svg.append("g").attr("transform", "translate(0,50)"));
pre {
display: none;
}
<script src="https://d3js.org/d3.v4.min.js"></script>
<svg width="500"></svg>
<pre id="csv">periodo,guadagno
2017-05-08,0.0
2017-05-09,0.5385
2017-05-10,0.0
2017-05-11,0.0
2017-05-12,0.0
2017-05-13,0.5680
2017-05-14,0.0
2017-05-20,0.0</pre>
Back to your code.
The solution is quite simple: using intervals. Let's set the interval for each tick:
d3.axisBottom(x).ticks(d3.timeDay)
Here is the same code with that change only:
var svg = d3.select("svg");
var data = d3.csvParse(d3.select("#csv").text());
var parseTime = d3.timeParse("%Y-%m-%d");
data.forEach(function(d) {
d.periodo = parseTime(d.periodo)
});
var x = d3.scaleTime()
.range([20, 480])
.domain(d3.extent(data, function(d) {
return d.periodo;
}));
var axis = d3.axisBottom(x).tickFormat(d3.timeFormat("%d/%m")).ticks(d3.timeDay)(svg.append("g").attr("transform", "translate(0,50)"));
pre {
display: none;
}
<script src="https://d3js.org/d3.v4.min.js"></script>
<svg width="500"></svg>
<pre id="csv">periodo,guadagno
2017-05-08,0.0
2017-05-09,0.5385
2017-05-10,0.0
2017-05-11,0.0
2017-05-12,0.0
2017-05-13,0.5680
2017-05-14,0.0
2017-05-15,0.0</pre>