# #ParisAttacks - How Twitter tells the story

This is an analysis of Twitter's hashtags after the week-end. I used a website (www.takwalker.com) to get the data. The dataset is aggregated for each hour of each days from Friday 13rd November 2015 to today. I chose to try to tell the story with Twitter's data.

# French Presidential election in 2012

This month, Tableau Public launch the Hacker Month which promote out of the ordinary vizzes. I chose to remake an old viz I have done 3 years ago about the Presidential election. This viz was created during the "inter-rounds weeks" and the aim was to simulate the final result: who will be the next president ?!

# Radar chart: I can see you...

After my last blog post about The Social Progress Index, I had a question about the creation of a radar chart. I will try to answer the question clearly during this blog post. On my own, I think radar chart is intersting if you want to compare members of a dimension in function of several metrics (you can also use Parallels coordinates). For example, when you want to buy a smartphone you can compare several devices with a radar chart (metrics: battery, camera, memory...). Let's try to explain how to create this in Tableau.

### Trigonometry, my best friend ever!

To create a radar chart, I have to use trigonometry formulas... You remember the circle with Pi and number and stuff like that... ?

"Unit circle angles color" by Jim.belk - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons.

Well... It is important to use it to create axis and it depends on number of metrics you want to display. Indeed, if you want to display 5 axis (= 5 metrics) you have to use differents formulas than 6 axis chart. In my case I used a 12 axis chart so I had to use several formulas (as on the image above).
Thanks to Internet I was able to find the different formulas and create a calculation in Tableau for X axis and Y axis.

Calculation for `[Xaxis]`
``````case [Dimension]
when "Member 1" then 0
when "Member 2" then [Value] *(1/2)
when "Member 3" then [Value] *(sqrt(3)/2)
when "Member 4" then [Value]
when "Member 4" then [Value] *(sqrt(3)/2)
when "Member 5" then [Value] *(1/2)
when "Member 6" then 0
when "Member 7" then [Value] *(-1/2)
when "Member 8" then [Value] *(-sqrt(3)/2)
when "Member 9" then [Value] *(-1)
when "Member 10" then [Value] *(-sqrt(3)/2)
when "Member 11" then [Value] *(-1/2)
end``````

Calculation for `[Yaxis]`
``````case [Dimension]
when "Member 1" then [Value]
when "Member 2" then [Value]*(sqrt(3)/2)
when "Member 3" then [Value]*(1/2)
when "Member 4" then 0
when "Member 5" then ([Value])*(-1/2)
when "Member 6" then [Value]*(-sqrt(3)/2)
when "Member 7" then [Value]*(-1)
when "Member 8" then [Value]*(-sqrt(3)/2)
when "Member 9" then [Value]*(-1/2)
when "Member 10" then 0
when "Member 11" then [Value]*(1/2)
when "Member 12" then [Value]*(sqrt(3)/2)
end``````

It is very important to have the same `[Value]` scale for each `[Dimension]` members! Indeed, the 12 axis have to be the same. In my case the scale was from 0 to 100.

### Build the radar to detect everything

After the creation of calculations, I had to build the chart. To do this, I just have to drag and drop the `[Yaxis]` on the lines shelf and the `[Xaxis]` on the columns shelf.

You can note that I use the aggregation Average (because Sum will returns a wrong result). Here I have only 1 point. To create the radar I have to use several dimensions (in my case, `[Country]` and `[IndexType]`). The `[IndexType]` allows me to draw 12 axis because this is a dimension with 12 members; `[Country]` allows me to draw 1 radar by country. If I want to draw the average radar chart, I can remove the `[Country]` field. To have several points I add [IndexType] on the Mark shelf as a Level of Detail.

After I can change the Mark to draw a polygon and add [Country] as a quick filter.

To have a beautiful radar, the last things to do are put [IndexType] as a Path to follow and Fix axis between -110 and 110 (or whatever you want to have enough space between borders and chart).

### Some Formatting and "VoilĂ "!

To give some design to my chart, I chose to remove grid lines, Zero lines and borders, and to hide headers. Moreover, I chose to give some trnasparency and a border to my polygon in order to have a more beautiful chart.

Finally, I drew a background image to have reference axis in order to give some visual impact. Indeed, I think it is better if you know where the maximum is.

To add beautiful tooltips, it is important to put AVG([Value]) on the Mark shelf and to configure the tooltip like this:

And "VoilĂ "! The radar chart is done!

# The Social Progress Index

Two weeks ago, I was browsing the Tableau community forum and I found an interesting question about reference line. The question was about to create a band reference line but just for few members in a dimension (Here is the question). This question drove me to an other question: Is it possible to create a "dynamic" reference line?

To answer it, I chose a dataset about Social metrics in the world: The Social Progress Index. With this dataset I tried to create a "dynamic" reference line.

As you can see in the visualisation below, when you click on a country on the map the reference line in the distribution graphic shows the average gap. The average gap is represented by a grey band calculated when the user click on a country. My idea was to show the gap when a country is highlighted and the average line in the other hand. To do this I used th LoD. It was just my second time with LoD... and it was very interesting!

The formula used in the LoD calculation allows me to calculate the general average: `{ EXCLUDE [Country]: avg([Value]) }`. To build the reference band, I chose the average for each country as the end and my LoD calculation as the begin. The 9.0 version of Tableau allows me to show re-calculated reference lines when a mark is selected so I used it to redraw the reference band! Because in fact, the band is equal to 0 when no selection is provided. After this I chose to add some other graphics such as the radar graph to show the shape of each country and a map to allow the selection.

# Analysis of Airbnb data

Thanks to Jewel Loree from Tableau Public, I found a dataset about Airbnb. The timing was excellent because I had to choose an Airbnb accomodation for a training in Luxembourg a few weeks ago. When I discovered the website Inside Airbnb, I was suprised to find a lot of CSV files concerning several cities around the world. As a French, I chose to start my analysis with Paris but actually, I downloaded all the files to build the visualisation below.

# History of the Eiffel Tower

IronViz time is here! This post is about my entry for the Wiki Contest. I have to admit that it was difficult to find a topic. First, I told me that it was too difficult to find a good and interesting topic with enough data and enough time to prepare these data... but in fact I found a topic yesterday evening during the Tableau User Group in Paris. During a conversation with co-leaders, they told me that we have to tell everybody : "French people do Tableau too !" That is why I choose to do a viz about The Eiffel Tower. I think it is a great construction and a great symbol for France!

You can find the viz just below. I tried to tell a story with the data of Wikipedia. I tried to present information about visitors, about the construction and the replicas. I put the sources just after the viz.