Develop Reference

d3.v5.min.js:2 Error: <path> attribute d: Expected moveto path command ('M' or 'm'), "function a(a){va…"

I am trying to plot a multi-line graph with d3.js but I am getting this error:
Error: attribute d: Expected moveto path command ('M' or 'm'), "function t(t){va…".
I have been stuck at it a while now and tried everything I could think of, to help you in your reflections, Find the code that I use below.
// set the dimensions and margins of the graph
var margin = {top: 10, right: 30, bottom: 30, left: 60},
width = 460 - margin.left - margin.right,
height = 400 - margin.top - margin.bottom;
const dateParser = d3.timeFormat("%Y-%m-%d %H:%M:%S");
data.forEach(function(d) {
d.ts = dateParser(new Date(d.ts));
d.value = parseFloat(d.value)
});
// append the svg object to the body of the page
var svg = d3.select("#graph")
.append("svg")
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.top + margin.bottom)
.append("g")
.attr("transform",
"translate(" + margin.left + "," + margin.top + ")");
//Read the data
// group the data: I want to draw one line per group
var sumstat = d3.nest() // nest function allows to group the calculation per level of a factor
.key(function(d) { return d.key;})
.entries(data);
// Add X axis --> it is a date format
var x = d3.scaleLinear()
.domain(d3.extent(data, function(d) { return d.ts; }))
.range([ 0, width ]);
svg.append("g")
.attr("transform", "translate(0," + height + ")")
.call(d3.axisBottom(x).ticks(5));
// Add Y axis
var y = d3.scaleLinear()
.domain([0, d3.max(data, function(d) { return +d.value; })])
.range([ height, 0 ]);
svg.append("g")
.call(d3.axisLeft(y));
// color palette
var res = sumstat.map(function(d){ return d.key }) // list of group names
var color = d3.scaleOrdinal()
.domain(res).range(['#e41a1c','#377eb8','#4daf4a','#984ea3','#ff7f00','#ffff33','#a65628','#f781bf','#999999'])
// Draw the line
svg.selectAll(".line")
.data(sumstat)
.enter()
.append("path")
.attr("fill", "none")
.attr("stroke", function(d){ return color(d.key) })
.attr("stroke-width", 1.5)
.attr("d", function(d){
return d3.line()
.x(function(d) { return x(d.ts); })
.y(function(d) { return y(d.value); })
})
I cannot figure what I am doing wrong, in case the example I am looking at is this link. I am fairly new to d3 and it is not an easy library to use

When you set the d attribute, you return the line generator itself from the data linking function, but you fail to execute it. Configuring the generator and executing it is a two-step process:
first, contruct and configure the generator (line is a function)
var line = d3.line()
.x(function(d) { return x(d.ts); })
.y(function(d) { return y(d.value); })
then, pass the function to attr(), so it will be executed as line(d)
svg.selectAll(".line")
.data(sumstat)
.enter()
.append("path")
.attr("fill", "none")
.attr("stroke", function(d){ return color(d.key) })
.attr("stroke-width", 1.5)
.attr("d", line)

Scaling y-axis appropriate to data in multiple line chart display

The multiple line chart example at https://www.d3-graph-gallery.com/graph/line_smallmultiple.html quite clearly provides the examples I need for what I'm trying to do...
except...
I need the y-axis scale for each of the charts to be appropriate for the data associated with the individual keys. As is, the example does d3.max on the entire data set, not the filtered data set controlling the individual lines.
I've tried various ways to apply the filter in the y-axis definition and can't get anything to work.
The closest I've been able to get is to make it use the max value from one of the specific keys for all the charts.
var y = d3.scaleLinear()
// .domain([0, d3.max(data, function(d) { return +d.n; })])
.domain([0, d3.max(data.filter(d => d.name === "Helen"), e => +e.n)])
.range([ height, 0 ]);
svg.append("g")
.call(d3.axisLeft(y).ticks(5));
I think I want it to filter d.name against the CURRENT-CHART key (whatever it might be) rather than a specific one (like "Helen" above), but can't figure out how to do it. Is it some feature of nesting that I haven't found yet? Something amazingly simple that I can't see??
Any suggestions?
Thanks in advance

I have built a demo for you, i hope you are looking for something like this. Please let me know if there is any issue.
// set the dimensions and margins of the graph
var margin = {top: 30, right: 0, bottom: 30, left: 50},
width = 210 - margin.left - margin.right,
height = 210 - margin.top - margin.bottom;
//Read the data
d3.csv("https://raw.githubusercontent.com/holtzy/data_to_viz/master/Example_dataset/5_OneCatSevNumOrdered.csv", function(data) {
// group the data: I want to draw one line per group
var sumstat = d3.nest() // nest function allows to group the calculation per level of a factor
.key(function(d) { return d.name;})
.entries(data);
// What is the list of groups?
allKeys = sumstat.map(function(d){return d.key})
// Add X axis --> it is a date format
var x = d3.scaleLinear()
.domain(d3.extent(data, function(d) { return d.year; }))
.range([ 0, width ]);
// color palette
var color = d3.scaleOrdinal()
.domain(allKeys)
.range(['#e41a1c','#377eb8','#4daf4a','#984ea3','#ff7f00','#ffff33','#a65628','#f781bf','#999999'])
// Add an svg element for each group. The will be one beside each other and will go on the next row when no more room available
var svg = d3.select("#my_dataviz")
.selectAll("uniqueChart")
.data(sumstat)
.enter()
.append("svg")
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.top + margin.bottom)
.append("g")
.attr("transform",
"translate(" + margin.left + "," + margin.top + ")")
.each(multiple);
svg
.append("g")
.attr("transform", "translate(0," + height + ")")
.call(d3.axisBottom(x).ticks(3));
// Add titles
svg
.append("text")
.attr("text-anchor", "start")
.attr("y", -5)
.attr("x", 0)
.text(function(d){ return(d.key)})
.style("fill", function(d){ return color(d.key) })
function multiple(item) {
var svg = d3.select(this);
var y = d3.scaleLinear()
.domain([0, d3.max(item.values, function(d) { return +d.n; })])
.range([height, 0]);
svg.append("g")
.call(d3.axisLeft(y).ticks(5));
var line = d3.line()
.x(function(d) { return x(+d.year); })
.y(function(d) { return y(+d.n); });
// Draw the line
svg
.append("path")
.attr("fill", "none")
.attr("stroke", function(d){ return color(d.key) })
.attr("stroke-width", 1.9)
.attr("d", line(item.values))
}
})
<!DOCTYPE html>
<meta charset="utf-8">
<!-- Load d3.js -->
<script src="https://d3js.org/d3.v4.js"></script>
<!-- Create a div where the graph will take place -->
<div id="my_dataviz"></div>

Creating a zoom function in D3

I have a function where that when a button is pressed (Several buttons the represent several animal types), that animal types SVG is updated with its corresponding data. I'm trying to replicate this zoom function but am having issues implementing it with my code. There are several SVGs that are used globally like this (one for each animal type):
let x = d3.scaleLinear()
.domain([0, 1000])
.range([ 0, width ]);
var xAxis = d3.axisBottom(x);
svgReptile.append("g")
.attr("transform", "translate(0," + height + ")")
.call(xAxis)
const yAxis = d3.scaleLinear()
.domain([0, 220])
.range([ height, 0])
svgReptile.append("g")
.call(d3.axisLeft(yAxis))
The function below is called when one of the animal buttons is pressed.
function update(animal, whatSVG, xAxis, yAxis, color) {
const points = whatSVG
.selectAll("circle")
.data(data);
points.enter()
.append("circle")
.attr("cx", function(d) {
return xAxis(d.state);
})
.attr("cy", function(d) {
return yAxis(d.percentage);
})
.merge(points)
.attr("r", 3)
.attr("cx", function(d) {
return xAxis(d.decade)
})
.attr("cy", function(d) {
return yAxis(d.count)
})
.style("fill", function (d) { return colour(d.animal) } );
points.exit()
.attr('r', 0)
.remove();
}
Question:
How can I implement a zoom feature that expands the x-axis when zoomed (or anything similar) like the one linked above?

I think you're looking for a 'brush zoom' from the last line of your question.
The following source code if from an example in a d3 graph gallery
The cross hair allows you to select an area to expand. If you follow the link there is a graph above it that is entitled "Zoom with axis" but it doesn't zoom in the way you've described, it just moves the axis, but doesn't enlarge the graph contents with it. Perhaps both will be useful!
Hope this helps
// set the dimensions and margins of the graph
var margin = {top: 10, right: 20, bottom: 20, left: 20},
width = 500 - margin.left - margin.right,
height = 400 - margin.top - margin.bottom;
// append the svg object to the body of the page
var Svg = d3.select("#brushZoom")
.append("svg")
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.top + margin.bottom)
.append("g")
.attr("transform",
"translate(" + margin.left + "," + margin.top + ")");
//Read the data
d3.csv("https://raw.githubusercontent.com/holtzy/D3-graph-gallery/master/DATA/iris.csv", function(data) {
// Add X axis
var x = d3.scaleLinear()
.domain([4, 8])
.range([ 0, width ]);
var xAxis = Svg.append("g")
.attr("transform", "translate(0," + height + ")")
.call(d3.axisBottom(x));
// Add Y axis
var y = d3.scaleLinear()
.domain([0, 9])
.range([ height, 0]);
Svg.append("g")
.call(d3.axisLeft(y));
// Add a clipPath: everything out of this area won't be drawn.
var clip = Svg.append("defs").append("svg:clipPath")
.attr("id", "clip")
.append("svg:rect")
.attr("width", width )
.attr("height", height )
.attr("x", 0)
.attr("y", 0);
// Color scale: give me a specie name, I return a color
var color = d3.scaleOrdinal()
.domain(["setosa", "versicolor", "virginica" ])
.range([ "#440154ff", "#21908dff", "#fde725ff"])
// Add brushing
var brush = d3.brushX() // Add the brush feature using the d3.brush function
.extent( [ [0,0], [width,height] ] ) // initialise the brush area: start at 0,0 and finishes at width,height: it means I select the whole graph area
.on("end", updateChart) // Each time the brush selection changes, trigger the 'updateChart' function
// Create the scatter variable: where both the circles and the brush take place
var scatter = Svg.append('g')
.attr("clip-path", "url(#clip)")
// Add circles
scatter
.selectAll("circle")
.data(data)
.enter()
.append("circle")
.attr("cx", function (d) { return x(d.Sepal_Length); } )
.attr("cy", function (d) { return y(d.Petal_Length); } )
.attr("r", 8)
.style("fill", function (d) { return color(d.Species) } )
.style("opacity", 0.5)
// Add the brushing
scatter
.append("g")
.attr("class", "brush")
.call(brush);
// A function that set idleTimeOut to null
var idleTimeout
function idled() { idleTimeout = null; }
// A function that update the chart for given boundaries
function updateChart() {
extent = d3.event.selection
// If no selection, back to initial coordinate. Otherwise, update X axis domain
if(!extent){
if (!idleTimeout) return idleTimeout = setTimeout(idled, 350); // This allows to wait a little bit
x.domain([ 4,8])
}else{
x.domain([ x.invert(extent[0]), x.invert(extent[1]) ])
scatter.select(".brush").call(brush.move, null) // This remove the grey brush area as soon as the selection has been done
}
// Update axis and circle position
xAxis.transition().duration(1000).call(d3.axisBottom(x))
scatter
.selectAll("circle")
.transition().duration(1000)
.attr("cx", function (d) { return x(d.Sepal_Length); } )
.attr("cy", function (d) { return y(d.Petal_Length); } )
}
})
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.13.0/d3.min.js"></script>
<div id="brushZoom"></div>

How to make a flat line in D3.js (version 3.x)

I have a graph which I can add a flat line with the following:
svg.append("line") // attach a line
.style("stroke", "black")
.attr("x", 60) // x position of the first end of the line
.attr("y1", 60) // y position of the first end of the line
.attr("x2", 60) // x position of the second end of the line
.attr("y2", 60);
However, this only crosses 1/3 of the graph. How do I add a flat line that will always go as far as the graph is long? Thanks

I assume you are using scales, at least for your date axis, so I would do something like this:
// Scales
const xScale = d3.scaleTime()
.range([0, 400])
.domain(d3.extent(data, d => new Date(d.date)))
const yScale = d3.scaleLinear()
.range([600, 0])
.domain([0, 100])
svg.append("line")
.style("stroke", "black")
.attr('x1', 0)
.attr('x2', 400)
.attr('y1', yScale(60))
.attr('y2', yScale(60))

You can add line to complete graph by using range function that you generated for making line chart.
line_straight = svg.append("line") // attach a line
.style("stroke", "black")
.attr("x", 0) // x position of the first end of the line
.attr("y1", yScale(0.8)) // y position of the first end of the line
.attr("x2", xScale(n-1)) // x position of the second end of the line
.attr("y2", yScale(0.8));
Below i am attaching my code. Here is the jsfiddle to the code. https://jsfiddle.net/nmks14ub/1/
// 2. Use the margin convention practice
var margin = {top: 50, right: 50, bottom: 50, left: 50}
, width = window.innerWidth - margin.left - margin.right // Use the window's width
, height = window.innerHeight - margin.top - margin.bottom; // Use the window's height
// The number of datapoints
var n = 21;
// 5. X scale will use the index of our data
var xScale = d3.scaleLinear()
.domain([0, n-1]) // input
.range([0, width]); // output
// 6. Y scale will use the randomly generate number
var yScale = d3.scaleLinear()
.domain([0, 1]) // input
.range([height, 0]); // output
// 7. d3's line generator
var line = d3.line()
.x(function(d, i) { return xScale(i); }) // set the x values for the line generator
.y(function(d) { return yScale(d.y); }) // set the y values for the line generator
.curve(d3.curveLinear) // apply smoothing to the line
// 8. An array of objects of length N. Each object has key -> value pair, the key being "y" and the value is a random number
var dataset = d3.range(n).map(function(d) { return {"y": d3.randomUniform(1)() } })
// 1. Add the SVG to the page and employ #2
var svg = d3.select("body").append("svg")
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.top + margin.bottom)
.append("g")
.attr("transform", "translate(" + margin.left + "," + margin.top + ")");
// 3. Call the x axis in a group tag
svg.append("g")
.attr("class", "x axis")
.attr("transform", "translate(0," + height + ")")
.call(d3.axisBottom(xScale)); // Create an axis component with d3.axisBottom
line_straight = svg.append("line") // attach a line
.style("stroke", "black")
.attr("x", 0) // x position of the first end of the line
.attr("y1", yScale(0.8)) // y position of the first end of the line
.attr("x2", xScale(n-1)) // x position of the second end of the line
.attr("y2", yScale(0.8));
// 4. Call the y axis in a group tag
svg.append("g")
.attr("class", "y axis")
.call(d3.axisLeft(yScale)); // Create an axis component with d3.axisLeft
// 9. Append the path, bind the data, and call the line generator
svg.append("path")
.datum(dataset) // 10. Binds data to the line
.attr("class", "line") // Assign a class for styling
.attr("d", line); // 11. Calls the line generator
.line {
fill: none;
stroke: #ffab00;
stroke-width: 3;
}
.overlay {
fill: none;
pointer-events: all;
}
/* Style the dots by assigning a fill and stroke */
.dot {
fill: #ffab00;
stroke: #fff;
}
.focus circle {
fill: none;
stroke: steelblue;
}
<!DOCTYPE html>
<meta charset="utf-8">
<body>
</body>
<!-- Load in the d3 library -->
<script src="https://d3js.org/d3.v5.min.js"></script>

Use of .on("mouseover", ...) in d3.js [duplicate]

This question already has answers here:
Why does click event handler fire immediately upon page load?
(4 answers)
Closed 4 years ago.
I'm getting introduced to javascript and I'm trying to use .on("mouseovert", ...) in order to get the x-value of my graph when the cursor is upon the graph.
My code look like this:
// do something as mouseover the graph
svg.select("svg")
.on("mouseover", alert("mouse on graph"));
The result is: an alert appears when I open the html file (and loading my js script), but nothing happen as is hover the graph.
Everything else in the script works fine.
Do you know why?
Thank you very much for the time you take!
Here is the full script:
function draw_co2(url) {
d3.select("svg").remove() //remove the old graph
// set the dimensions and margins of the graph
var margin = {
top: 20,
right: 20,
bottom: 30,
left: 50
},
width = 960 - margin.left - margin.right,
height = 500 - margin.top - margin.bottom;
// parse the date / time
var parseTime = d3.timeParse("%Y-%m-%d");
// Get the data
d3.json(url, function (error, data) {
if (error)
throw ('There was an error while getting geoData: ' + error);
data.forEach(function (d) {
d.Date = parseTime(d.Date);
d.Trend = +d.Trend;
});
// set the ranges // Scale the range of the data
var x = d3.scaleTime().domain([new Date("1960"), new Date("2015")]).range([0, width]);
var y = d3.scaleLinear()
.domain([d3.min(data, function (d) {
return d.Trend;
}) - 1 / 100 * d3.min(data, function (d) {
return d.Trend;
}), d3.max(data, function (d) {
return d.Trend;
}) + 1 / 100 * d3.min(data, function (d) {
return d.Trend;
})])
.range([height, 0]);
// define the line
var valueline = d3.line()
.x(function (d) {
return x(d.Date);
})
.y(function (d) {
return y(d.Trend);
});
// append the svg obgect to the body of the page
// appends a 'group' element to 'svg'
// moves the 'group' element to the top left margin
var svg = d3.select("#graph_draw").append("svg")
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.top + margin.bottom)
.append("g")
.attr("transform",
"translate(" + margin.left + "," + margin.top + ")");
//Y Axis label
svg.append("g")
.call(d3.axisLeft(y))
.append("text")
.attr("fill", "#000")
.attr("transform", "rotate(-90)")
.attr("y", 6)
.attr("dy", "0.71em")
.attr("text-anchor", "end")
.text("Carbon dioxide (ppm)");
// Add the valueline path.
svg.append("path")
.data([data])
.style("opacity", 0)
.transition()
.duration(1000)
.style("opacity", 1)
.attr("class", "line")
.attr("d", valueline);
// Add the X Axis
svg.append("g")
.attr("transform", "translate(0," + height + ")")
.call(d3.axisBottom(x));
// Add the Y Axis
svg.append("g")
.call(d3.axisLeft(y));
// gridlines in x axis function
function make_x_gridlines() {
return d3.axisBottom(x)
.ticks(10);
};
// add the X gridlines
svg.append("g")
.attr("class", "grid")
.attr("transform", "translate(0," + height + ")")
.call(make_x_gridlines()
.tickSize(-height)
.tickFormat(""));
// do something as mouseover the graph
svg.select("svg")
.on("mouseover", alert("mouse on graph"));
})
}

Use mouser over as an inline function
svg.select("svg")
.on("mouseover", function () {
alert("mouse on graph")
});