Develop Reference

How to make a smooth transition in a pie chart when updating values in d3?

I am using j3.ds to deploy some data on a pie chart. It seems to work fine and it updates correctly when I introduce new data. The thing is, I wanted to do the transition when updating smoothly, like here:
https://www.d3-graph-gallery.com/graph/pie_changeData.html
For some reason it is not working when I introduce the merge and transition, can somebody help with the task? thanks in advance
update();
function update() {
var data = d3.selectAll('.values').nodes();
var pie = d3.pie() //we create this variable, for the values to be readeable in the console
.value(function(d) {return d.innerHTML; })(data);
console.log("pie = ",pie)
var u = svg.selectAll("path")
.data(pie)
console.log("u = ",u)
// Build the pie chart: Basically, each part of the pie is a path that we build using the arc function
u
.enter()
.append('path')
.merge(u)
.transition()
.duration(2000)
.attr('d', d3.arc()
.innerRadius(0)
.outerRadius(radius)
)
.attr('fill', function(d,i){ return color[i] })
.attr("stroke", "black")
.style("stroke-width", "2px")
.style("opacity", 1)
}

Merge combines one selection with another as follows:
selectionCombined = selection1.merge(selection2);
You aren't providing a second selection, so you aren't merging anything. The selection you do have you are calling .merge() on is the enter selection, returned by .enter() - unless you add new slices to the pie, this will be empty every update after the first. As you aren't merging anything with the enter selection, post merge the selection is still empty.
The enter selection is used to create elements so that for every item in the data array there is one corresponding element in the DOM - as you already have slices, only the update selection is not empty.
The update selection is that returned by .data(), it contains existing elements which correspond to items in the data array. You want to merge this selection with the one returned by .enter():
var update = svg.selectAll("path")
.data(pie)
var enter = update.enter()
.append('path')
var merged = update.merge(enter)
However, a transition needs a start value and an end value. In your case you are trasitioning the d attribute of a path. On update the start value is the path's current d and the end value is a d representing the new value for the slice. On initial entry, what is the value that the transition should start from? It may be more appropriate to only transition on update:
var arc = d3.arc().innerRadius(0).outerRadius(radius);
var update = svg.selectAll("path")
.data(pie)
var enter = update.enter()
.append('path')
// Set initial value:
.attr('d', arc)
// If these values don't change, set only on enter:
.attr('fill', function(d,i){ return color[i] })
.attr("stroke", "black")
.style("stroke-width", "2px")
update.transition()
// transition existing slices to reflect new data.
.attr('d',arc)
Note: transitioning paths can be difficult - you'll notice the deformity to the pie in the transition in your example. This is because of how the d attribute string is interpolated. If you want to preserve the radius a different approach is needed in applying the transition.

D3 - forEach is not a function when upgrading from v3 to v4

I am trying to upgrade this stackable bar chart to v4.
Everything works except for one thing.
When I filter one category the bars don't drop to the start of the x-axis. I get an error which says:
state.selectAll(...).forEach is not a function
I've tried multiple things but I can't figure this one out.
This is the broken code:
function plotSingle(d) {
class_keep = d.id.split("id").pop();
idx = legendClassArray.indexOf(class_keep);
//erase all but selected bars by setting opacity to 0
d3.selectAll(".bars:not(.class" + class_keep + ")")
.transition()
.duration(1000)
.attr("width", 0) // use because svg has no zindex to hide bars so can't select visible bar underneath
.style("opacity", 0);
//lower the bars to start on x-axis
state.selectAll("rect").forEach(function(d, i) {
//get height and y posn of base bar and selected bar
h_keep = d3.select(d[idx]).attr("height");
y_keep = d3.select(d[idx]).attr("y");
h_base = d3.select(d[0]).attr("height");
y_base = d3.select(d[0]).attr("y");
h_shift = h_keep - h_base;
y_new = y_base - h_shift;
//reposition selected bars
d3.select(d[idx])
.transition()
.ease("bounce")
.duration(1000)
.delay(750)
.attr("y", y_new);
})
}
I find it strange that this works flawlessly in D3 v3, why wouldn't this work in v4?

In d3 v3 selectAll returned an array, in d3 v4 it returns an object.
From the v3 notes:
Selections are arrays of elements—literally (maybe not literally...).
D3 binds additional methods to the array so that you can apply
operators to the selected elements, such as setting an attribute on
all the selected elements.
Where as changes in v4 include:
Selections no longer subclass Array using prototype chain injection;
they are now plain objects, improving performance. The internal fields
(selection._groups, selection._parents) are private; please use the
documented public API to manipulate selections. The new
selection.nodes method generates an array of all nodes in a selection.
If you want to access each node in v4 try:
selection.nodes().forEach( function(d,i) { ... })
But, this is just the node, to get the data you would need to select each node:
var data = [0,1,2];
var svg = d3.select("body").append("svg")
.attr("width",500)
.attr("height",200)
var circles = svg.selectAll("circle")
.data(data)
.enter()
.append("circle")
.attr("cx", function(d,i) { return i * 20 + 50 })
.attr("cy", 50)
.attr("r", 4);
circles.nodes().forEach(function(d,i) {
console.log(d3.select(d).data());
})
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.10.0/d3.min.js"></script>
But, if you need the data or to modify the selection properties, it could be easier to use selection.each(). d3.each iterates through each element of a d3 selection itself, and allows you to invoke a function for each element in a selection (see API docs here):
var data = [0,1,2];
var svg = d3.select("body").append("svg")
.attr("width",500)
.attr("height",200)
var circles = svg.selectAll("circle")
.data(data)
.enter()
.append("circle")
.attr("cx", function(d,i) { return i * 20 + 50 })
.attr("cy", 50)
.attr("r", 4);
circles.each( function() {
console.log(d3.select(this).data());
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.10.0/d3.min.js"></script>
In v3 of this bar chart, in the forEach loop
`states.selectAll("rect").forEach(function(d,i) {`
d is an array of nodes (the rectangles in each .g).
But, in v4 d3 selections aren't arrays, you can't use a forEach loop in the same way. But you can still get the nodes in it without much modification using selection.nodes() and than get the childNodes to replicate the array in the v3 version:
state.nodes().forEach(function(d, i) {
var nodes = d.childNodes;
Here we go through each element/node in state and get the child rects, returned as an array. Here's an updated fiddle.

D3 Data join with containers

How do I properly do data joins with wrapper elements on some of the levels? For instance, say I have the data [[a,b],[x,y]] and I want to transform it to this:
<wrapper1>
<content1>
<wrapper2>
<content2>a</content2>
</wrapper2>
<wrapper2>
<content2>b</content2>
</wrapper2>
</content1>
</wrapper1>
<wrapper1>
<content1>
<wrapper2>
<content2>x</content2>
</wrapper2>
<wrapper2>
<content2>y</content2>
</wrapper2>
</content1>
</wrapper1>
Is there a standard way to create elements with this structure?

Here is a code that creates that exact tree structure.
The outerSelection uses as data the outer array, which has 2 elements: [a, b] and [x, y].
Then, the innerSelection uses as data the inner arrays, each one containing two elements: "a" and "b" for the first one and "x" and "y" for the second one.
Click "Run conde snippet" and look at your console (the console of your browser, which you can expand, not the snippet's one):
var body = d3.select("body");
var data = [
["a", "b"],
["x", "y"]
];
var outerSelection = body.selectAll(null)
.data(data)
.enter()
.append("wrapper1")
.append("content1");
var innerSelection = outerSelection.selectAll(null)
.data(function(d) {
return d
})
.enter()
.append("wrapper2")
.append("content2")
.html(function(d) {
return d
})
console.log(body.node())
<script src="https://d3js.org/d3.v4.min.js"></script>

You can achieve this by using the d3 'data' function. As you have two levels of data here, this is how I would do it:
data = [['a','b'],['x','y']];
d3.select("#div1")
.selectAll("wrapper1")
.data(data)
.enter().append("wrapper1")
.attr("d", function (d) {
d3.select(this)
.selectAll("content1")
.data(d)
.enter().append("content1")
.attr("d", function (d2) {
d3.select(this)
.append("wrapper2")
.append("content2")
.html(d2);
})
});
JSFiddle

Using D3's path generators. How to assign data to them?

I'm currently trying to implement a line-graph with D3.js
The D3-documentation contains the following examples:
var line = d3.svg.line()
.x(function(d) { return d.x; })
.y(function(d) { return d.y; })
.interpolate("basis");
g.append("path")
.attr("d", line);
... and says "Whatever data is bound to g (in this example) will be passed to the line instance."
What is meant with "bounding data"?
I've got the following code which works:
var lineGen = d3.svg.line()
.x(function(d, i) {
return xScale(i);
})
.y(function(d) {
return HEIGHT - yScale(d);
})
.interpolate('basis');
var lineVal = lineGen(data);
svg.append('path').attr('d', lineVal)
.attr({
'fill': 'none',
'stroke': 'black',
'stroke-width': '3'
});
With lineGen(data) I generate a string. Then I assign this string to the attr-setter.
But the way which is explained in the official documentation doesn't work.
What do I have to do to bound my data to the SVG element directly?
svg.data(data) doesn't work. I've tried that already.
UPDATE
I've found the solution in a tutorial.
// Data-structure. In this case an
// one-dimensional array.
var data = [ 22, 31, 29, 32, 21, 38, 30 ];
svg.append('path')
// Assign the data-structure as ONE
// element an array-literal.
.data([data])
.attr('d', lineGen)
.attr({
'fill': 'none',
'stroke': 'black',
'stroke-width': '3'
});
By assigning the data-structure as an element of an array-literal the
whole data are bound to one element.
An alternative to this technique is the usage of selection.datum().
https://github.com/mbostock/d3/wiki/Selections#datum

In d3 data is bond to the selections. You can use enter and exit selections to create new nodes for incoming data and remove outgoing nodes that are no longer needed.
In your example, you should try as shown below.
var line = d3.svg.line()
.x(function(d) { return d.x; })
.y(function(d) { return d.y; })
.interpolate("basis");
g.selectAll("path") //Selects all the elements that match the specific selector, here elements having path tag
.data(data) //The data operator joins the specified array of data with the current selection.
.enter() //The enter selection contains placeholders for any missing elements. Here it has placeholders for n path elements where n is the length of data array.
.append("path") //For each placeholder element created in the previous step, a path element is inserted.
.attr("d", line); //The first param of line function would be the data (corresponding array element) bond to the current path element. And the second param is the data index.
To know more about data binding in d3 refer : Binding-data-to-dom-elements.
Edit :
To create a single path element with data bonded, try as shown below.
g.append("path")
.datum(dataObj) //Where dataObj is data[i]
.attr("d", line);

multiple circles / lines using d3.js

I have a d3.js problem and have struggled with this for a while and just can not seem to solve it. I believe it is pretty easy, but am missing something very basic.
Specifically, I have the following code, which generates a line and 2 circles for the 1st entry in the JSON - I have 'hardcoded' it for the first entry.
I'd like to now add the 2nd and 3rd entries of the JSON file to the graph and have control over line and circle colors and then generalize the code.
From reading the documentation and StackOverflow, it seems like the proper approach is to use nesting, but I can't seem to make it work?
The code is on jsfiddle at the following URL and the javascript is below.
http://jsfiddle.net/GVmVk/
// INPUT
dataset2 =
[
{
movie : "test",
results :
[
{ week: "20130101", revenue: "60"},
{ week: "20130201", revenue: "80"}
]
},
{
movie : "beta",
results :
[
{ week: "20130101", revenue: "40"},
{ week: "20130201", revenue: "50"}
]
},
{
movie : "gamm",
results :
[
{ week: "20130101", revenue: "10"},
{ week: "20130201", revenue: "20"}
]
}
];
console.log("1");
var parseDate = d3.time.format("%Y%m%d").parse;
var lineFunction = d3.svg.line()
.x(function(d) { return xScale(parseDate(String(d.week))); })
.y(function(d) { return yScale(d.revenue); })
.interpolate("linear");
console.log("2");
//SVG Width and height
var w = 750;
var h = 250;
//X SCALE AND AXIS STUFF
//var xMin = 0;
//var xMax = 1000;
var xScale = d3.time.scale()
.domain([parseDate("20130101"),parseDate("20131231")])
.range([0, w]);
console.log(parseDate("20130101"));
console.log("3");
var xAxis = d3.svg.axis()
.scale(xScale)
.orient("bottom");
console.log("4S");
//Y SCALE AND AXIS STUFF
var yScale = d3.scale.linear()
.domain([0, 100])
.range([h, 0]);
var yAxis = d3.svg.axis()
.scale(yScale)
.orient("left")
.ticks(5);
//Create SVG element
var svg = d3.select("body")
.append("svg")
.attr("width", w)
.attr("height", h);
console.log("4S1");
//CREATE X-AXIS
svg.append("g")
.attr("class", "axis")
.attr("transform", "translate(0," + (h - 30) + ")")
.call(xAxis);
//Create Y axis
svg.append("g")
.attr("class", "axis")
.attr("transform", "translate(" + 25 + ",0)")
.call(yAxis);
svg.selectAll("circle")
.data(dataset2[0].results)
.enter()
.append("circle")
.attr("cx", function(d) {
// console.log(d[0]);
console.log(parseDate(d.week));
return xScale(parseDate(d.week));
})
.attr("cy", function (d) {
return yScale(d.revenue);
})
.attr("r", 3);
//create line
var lineGraph = svg.append("path")
.attr("d", lineFunction(dataset2[0].results))
.attr("class", "line");

The word "nesting" comes up in two contexts in d3 -- creating nested data arrays with d3.nest, and using nested data to create nested selections.
Your data is already in the correct format for a nested selection -- an array of objects, each of which has a sub-array of individual data points. So you don't need to worry about manipulating the data, you just need to go straight to joining your data to your elements in nested d3 selections:
I'm going to take you through it quickly, but the following tutorials will be good reference for the future:
Thinking with Joins
Nested Selections
How Selections Work
On to your example: you have a top-level data structure that is an array of movie objects, each of which contains a sub-array of weekly revenue values. The first thing you need to decide is what type of elements you want associated with each level of data. You're drawing a line and a set of circles for the data in the sub-array, but aren't currently adding anything for the top-level array objects (the movies). You need to add something for them in order for nested selections to work, and it needs to be something that can contain your line and circle. In SVG, that's almost always going to be a <g> (grouping) element.
To efficiently create one <g> element for every object in your data array -- and to attach the data objects to the elements for future reference -- you create an empty selection, join your data to it, then use the enter() method of the data join selection to add elements for each data object that didn't match an element. In this case, since we don't have any elements to start, all the data objects will be in the enter() selection. However, the same pattern also works when updating some of the data.
var movies = svg //start with your svg selection,
//it will become the parent to the entering <g> elements
.selectAll("g.movie") //select all <g> elements with class "movie"
//that are children of the <svg> element
//contained in the `svg` selection
//this selection will currently be empty
.data( dataset2 ); //join the selection to a data array
//each object in the array will be associated with
//an element in the selection, if those elements exist
//This data-joined selection is now saved as `movies`
movies.enter() //create a selection for the data objects that didn't match elements
.append("g") //add a new <g> element for each data object
.attr("class", "movie") //set it's class to match our selection criteria
//for each movie group, we're going to add *one* line (<path> element),
//and then a create subselection for the circles
.append("path") //add a <path> within *each* new movie <g> element
//the path will *inherit* the data from the <g> element
.attr("class", "line"); //set the class for your CSS
var lineGraph = movies.select("path.line")
//All the entered elements are now available within the movies selection
//(along with any existing elements that we were updating).
//Using select("path") selects the first (and only) path within the group
//regardless of whether we just created it or are updating it.
.attr("d", function(d){ return lineFunction(d.results); });
//the "d" attribute of a path describes its shape;
//the lineFunction creates a "d" definition based on a data array.
//If the data object attached to the path had *only* been the d.results array
//we could have just done .attr("d", lineFunction), since d3
//automatically passes the data object to any function given as the value
//of an .attr(name, value) command. Instead, we needed to create an
//anonymous function to accept the data object and extract the sub-array.
var circles = movies.selectAll("circle")
//there will be multiple circles for each movie group, so we need a
//sub-selection, created with `.selectAll`.
//again, this selection will initially be empty.
.data( function(d) {return d.results; });
//for the circles, we define the data as a function
//The function will be called once for each *movie* element,
//and passed the movie element's data object.
//The resulting array will be assigned to circles within that particular
//movie element (or to an `enter()` selection, if the circles don't exist).
circles.enter() //get the data objects that don't have matching <circle> elements
.append("circle") //create a circle for each
//the circles will be added to the appropriate "g.movie"
//because of the nested selection structure
.attr("r", 3); //the radius doesn't depend on the data,
//so you can set it here, when the circle is created,
//the same as you would set a class.
circles //for attributes that depend on the data, they are set on the entire
//selection (including updating elements), after having created the
//newly entered circles.
.attr("cx", function(d) { return xScale( parseDate(d.week) ); })
.attr("cy", function(d) { return yScale( d.revenue ); });
Live version with the rest of your code: http://jsfiddle.net/GVmVk/3/
You'll need to adjust the domain of your x-scale so that the first data points aren't cut off, and you'll need to decide how you want to use your movie title property, but that should get you going.

Yes indeed, nested selection are the way to go for the circles, although you don't need them for the paths:
svg.selectAll("g.circle")
.data(dataset2)
.enter()
.append("g")
.attr("class", "circle")
.selectAll("circle")
.data(function(d) { return d.results; })
.enter()
.append("circle")
.attr("cx", function(d) {
// console.log(d[0]);
console.log(parseDate(d.week));
return xScale(parseDate(d.week));
})
.attr("cy", function (d) {
return yScale(d.revenue);
})
.attr("r", 3);
//create line
var lineGraph = svg.selectAll("path.line")
.data(dataset2).enter().append("path")
.attr("d", function(d) { return lineFunction(d.results); })
.attr("class", "line");
Complete example here.