#TweakThursday 23: Creating Trochoids with 2 Rows of Data

Following previous post on Creating Sigmoid with 2 Rows of Data which is inspired by Rody Zakovich's post, I was looking for some interesting curves to apply the same trick. Then I fell on this one:
http://www.tableau.com/stories/gallery/theta-analysis
This viz is created by the technical product marketing people at Tableau. The trochoids are defined here which belong to a family of math functions.

The twbx file weighs over 12MB and there are 880K+ rows in the data set. Looks like a good case for me to try. The result is pretty good. To create the same chart, I only needed 2 rows of data in a single column. The workbook size is reduced to 118K, that is, less than 1% of the original size.

The key for the data reduction is the use of data densification.

Click image to view the interactive version.

Some details of the implementation are as follows.

1.The two rows of data are in a single column:

2.I created "gear ratio" and "cycloidality ratio" as parameters, instead of dimensions. This saves quite a few rows

3.Used Padded and Index() to create data densification as did in the previous post.

4.Created 5 calculated fields for the coordinates:

That's the tweak of the week.

(Refresh the page if you want to view the gif image multiple times. Or go to Tableau Public and click the button at the top-right corner.)

Jake and I collaborated on a dashboard. He told me that he learnt a way to create an in-place help page in Tableau. He first saw it at a conference somewhere and couldn't recall who the speaker was. So I am blogging here about it but the credit goes to somebody else. If anyone knows who the original creator is, leave a comment below.

The key idea is to float a semi transparent worksheet on top of the dashboard, where a help text box is strategically placed on top of each chart. This way, we can explain how to view each chart and what data points are important, etc. This worksheet is collapsible by a show/hide button.

Below I would like to show how this worksheet can be constructed.

1. Sheet with a single data mark.

Double click the empty space in Marks panel and add two single quotes. Make the null pill a text label. This creates a single null mark.
Set the view as "Entire View"

2. Create an show/hide button

Go to the target dashboard
Drag a floating vertical container to the dashboard, making it cover all the area of interest.
Drag the Single Null Mark sheet and drop it into the above container. Hide the sheet title.
Create an open/close button for the container and place the button at the top-right corner.

3. Add annotations

Format the sheet background opacity as 70% in the layout manager
Select area annotations and place them anywhere of interest.
Write help text and format it to highlight important messages.
The text can serve as functional guide and/or insight guide.

Here is an example. Feel free to download the workbook and explore. Click the "i" button at the top-right corner to view the in-place help.

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Vizible Difference

In search of data visualization excellence

1. Sheet with a single data mark.

2. Create an show/hide button

3. Add annotations

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