VizWiz

Data Viz Done Right

May 19, 2014

Makeover Monday: India's BSE Sensex as an Area Chart

3 comments

I'm not a huge fan of area charts, especially stacked area charts. Much like bar charts, the axis for an area chart needs to start at zero, otherwise you're not showing the total area, thus defeating the purpose of using an area chart in the first place.

As an example, here's a recent chart from Chart of the Day about India's stock market.

Notice how they've started the axis at 2,600. This distorts the slope of the graph and also the area of the graph is not complete.

Contrast this to Yahoo!'s chart, which is executed perfectly.

2014-05-19_09-18-12

Yahoo! is showing the entire scale and nice proportions. Without noticing these subtle differences, you might interpret a very different story. Moral of the story: always start the axis for area charts at zero.

May 16, 2014

Tableau Tip: How the familiar Windows Right-click+Drag, CTRL+Drag and Shift+Drag work on Tableau for Mac

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Most people that have been using Tableau for years have become very familiar with right-click+dragging pills to bring up context menu (particularly for dates), plus lots of other keyboard shortcuts. The Mac OS works differently, so if you're considering switching to Tableau for Mac, here are some handy tips to keep in mind (via this response by Vijay Doshi on the Tableau Forums):

The Option+Left Click is necessary because Mac and windows handle the right-click event slightly differently.

On windows there are effectively two events:

    1. On right-click press down, no menu is shown and you can then drag the pill around.
    2. On right-click release, Tableau shows the "right-click menu".

On Mac, the convention is on right-click press down you see the context menu (try it in finder). Tableau cannot show both the context menu and drag. Thus, Tableau has to use a keyboard modifier.

Command+Drag will duplicate a field (i.e., copying the same field from/to a shelf from/to LOD). On Windows this is Control+Drag (Tableau could not keep it the same because on Mac Control+Left-click = context menu by convention).

Option+Drag will show you the aggregation options for the field.

One bug that I've reported is that when you Command+Drag to duplicate a field, you won't see the little + that you do on Windows that is a visual clue that you're duplicating the field.

May 12, 2014

Makeover Monday: Will Johnny Manziel stop the run of terrible QBs for the Cleveland Browns?

5 comments

The NFL Draft is somewhat of a national holiday here in the US. It’s the day when all fans can dream of their team using their picks to turn the fortunes of their franchise around. QBs are particularly in the spotlight. In this spirit, Chart of the Day published a chart on Friday after the first round of the NFL Draft showing the number of starting QBs for each NFL team since 1999.

Accompanying the chart was this statement:

“Since 1999, 20 different quarterbacks have started for the Browns, the most in the NFL. Meanwhile, the New England Patriots have had just three starting quarterbacks over the same span.”

This statement implies that there is a relationship between number of starting QBs and success (because they’re only talking about the outliers), yet they provide no additional context. I downloaded the winning percentages for every NFL team since 1999 from SportingCharts.com and joined it to the Chart of the Day data. 

I like how they’ve sorted the bars in ascending order by number of QBs, yet I don’t like how they always have the labels rotated. A horizontal bar chart would be much easier to read.

Given that we can easily compare number of QBs and win %, I turned to Tableau and build this simple view.

Looking at the data this way, it becomes much more clear that there is no direct correlation between the number of starting QBs and win % (as implied by COTD).

  • Detroit is an absolutely horrible franchise, yet they’re right in the middle of the pack with starting QBs. 
  • Chicago has a winning record, yet they’ve used the third most QBs.
  • Cincinnati and Houston have had pretty stable QB situations, yet they don’t win even half of their games.

One particular insight that sticks out to me is the amazing amount of parity that exists in the NFL. 25 or 32 teams have between 40-60% win percentage. In any given season, you can pretty much count on around 80% of the teams winning between 9.6 and 6.4 games per season. This is exactly what the NFL wants and is a large reason that they run a socialist type model of revenue sharing.

What else do you see? You can click on a team to highlight them. Download the data here and the workbook here.

May 5, 2014

Makeover Monday: Vaccine-Preventable Outbreaks

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The Council on Foreign Relations maintains this map, sponsored by the wonderful Bill & Melinda Gates Foundation, that “plots global outbreaks of diseases that are easily preventable by inexpensive and effective vaccinations.”

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Click on the map to interact.

Of course, there’s no way that you can criticize the cause, but the map itself suffers from several basic flaws:

  1. The data is pretty messy. I’m not sure how they were able to categorize data into years in their map. They might be showing the same dot in multiple years. I took the liberty to clean up the data a bit.
  2. The color of the bubbles on their map are too strong and there’s no transparency. There are dots behind dots, but you would never know it.
  3. The size of the bubbles are not relative to each other. For example, there are ten cases of measles in northeast Brazil and the dot immediately below represents 138 cases. Clearly the lower dot is not 13 times larger as it should be.
  4. When you click on a Region on the left filter of their map, the map doesn’t actually filter, it merely repositions.

There are lots of other issues too, but I’ll stop there; you get the idea.

It’s great that they make the data available, as they should, so kudos to the foundation for that. I created the version below to communicate the story more effectively. 

I believe I have addressed the sizing and colors of the bubbles issues. I’ve also added bar charts to provide a high-level overview of diseases and impact. Finally, I’ve made different metrics available. Their version only showed cases, where they also provided fatality data. Therefore, I included fatalities and fatality rate metrics.

Last, but not least, I wanted to give a special thank you to Emily Kund for her feedback!

May 3, 2014

#SFBATUG: Using a calendar widget to control your dashboard

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Last night at the SFBATUG meet up, I had the pleasure of giving a hands-on demo of how to create an interactive calendar in Tableau.  This is a follow up to a post I write in May 2012 detailing how to create the calendar

This example goes a step farther in that I’m using the calendar like a widget to control what I’m seeing on my dashboard.  What’s also cool about this method is that you can multi-select dates, something you can’t currently do with date quick filters.

Note that I also demoed how to hide a reference line behind a bar, which I wrote about here.

Finally, this dashboard is not a stellar example of design.  I threw this together quickly so that I could share it with the community promptly.

Download the workbook here.