# Assignment 5

• Posting date: 2019-09-24
• Due date: 2019-10-01 11:59PM
• GitHub Classroom link: Assignment 5

# Description

In this assignment, you will improve your code for the visualization scatterplot_1 you built last week. You will use a variety of d3 features:

• d3 scales for:
• circle positions
• circle colors
• d3 axes
• d3 transitions

You are welcome to use the code you submitted for Assignment 4, or to start with code from scratch. But the new submission will have to use the d3 features shown above.

Just like the plot in Assignment 4, the id attribute of your div should be scatterplot_1.

## 1. D3 Scales: 85% credit

Somewhere in your code for assignment 4, there’s very probably some code that looks like this:

svg.selectAll("circle")
.attr("cx", function(d) { /* SOME CODE HERE */ })
.attr("cy", function(d) { /* SOME CODE HERE */ });


### 1a. Circle Positions: 25% credit

In this part of the assignment, you will write the selection update code so that it look like this:

svg.selectAll("circle")
.attr("cx", function(d) { return cxScale(d.SATM); })
.attr("cy", function(d) { return cyScale(d.SATV); });


Notice that we’re explicitly calling two separate functions, cxScale and cyScale. In your code, define variables cxScale and cyScale to be instances of d3.scaleLinear(), configured appropriately.

### 1b. Circle Radii: 15% credit

Do the same thing for the r attribute of your circles: make the update code refer to a rScale variable, and then define it appropriately. Here, however, use d3.scaleSqrt (This is a better choice to control the area of a circle - as we will see in class, it is generally better to use area to control the size of a shape). The smallest circles should have radius 10, and the largest circles, radius 20.

### 1c. Circle colors: 45% credit

You will implement a number of colormaps variations. Add buttons to your visualization to toggle these colormaps (See this minimal example to learn how to use d3 to create buttons in your HTML page that react to when you click on them.)

1) Create a continuous color scale that interpolates linearly from the minimum SATV in the data being given color red, to the maximum SATV in the data being given color green.

2) Create a continuous color scale that uses three of the colors in RdYlGn-5 as follows. The minimum SATV should be given #d7191c (the first color), the average SATV should be given #ffffbf (the third color), and the maximum SATV should be given #1a9641 (the fifth color). HINT: read the documentation on d3 scales.

3) Create a quantized color scale that uses all five colors in RdYlGn-5 such that the minimum SATV gets the red color, the maximum SATV gets the green color, and there are five “bands” of SATV values each mapped to one of the colors. HINT: read the documentation on d3 quantize scales.

Your buttons should have the following ids: colormap-button-1, colormap-button-2, and colormap-button-3. Their behavior should be such that when we click on the button, the points in the visualization switch to the corresponding colormap.

## 2. D3 Axes: 10% credit

Next, you will add d3 axis annotations to this same scatterplot, by using the objects d3.axisLeft() and d3.axisBottom(). Follow the example here (search for “axisBottom”). Note that d3 axes use some pre-defined CSS classes by default. The easiest way to make the axes plot the way you want is to add CSS declarations to your HTML. Again, follow the example above.

## 3. Animated Transitions: 5% credit

When changing the circle colors, make the change an animated transition of duration 3 seconds, using d3 transitions.

## 4. Extra credit: Position transitions (10% extra credit)

Add two buttons to your webpage that will toggle the x position of your circles, alternating between SATM (the value you started with above) and the cumulative score, SATM + SATV. The button to choose SATM values should have id SATM, and the button for the cumulative score should have id SAT-cumulative. Note that these two data attributes have significant different ranges, and you should make the position scale of both cases “nice”: in other words: the SATM scale should range from 300 to 800, but the SATM + SATV scale should range from 600 to 1600. Make this an animated transition.

For full credit, the axes ticks and marks will need to be animated as well! HINT: this is way, way, easier than it seems; d3 does what you would hope for here.