A colleague posted this: "Hi Team, may I ask if you have any good idea to show the % difference of two randomly selected data points on a line chart?"

I found a solution to it, which is as follows.

- Click to set one point as a reference
- Hover over another point 
- Show the difference between the two points in tooltips

Both click and hover are actions that allow us to save a point's attributes into parameters. Then we can calculate the difference easily.

Here are the detailed steps of implementation.

Click to set a reference point

Each point has 3 attributes:
- Sub-Category
- Date
- Sales value

Being a reference point, all three attributes need to be stored in parameters.

Create one parameter for each of the attributes. For the reference point, we need three parameters. Set up one parameter action for each of them.
Here is how we create a parameter action for saving the reference sub-category into a string parameter called Reference Sub Category. 
We need to do the same for saving the other two attributes into Reference Date and Reference Sales parameters. Details can be found in the companion workbook.

Hover over a point of interest

By hovering the mouse over a point of interest which we want to compare against the reference point, we will trigger the following actions:
- Save the two attributes of the point Sub-Category and Date into two parameters with parameter actions. 
- Calculate the difference between this point and the reference point. Show them in tooltips. Here is the formula:

Highlight both points with bigger size and different colors

To highlight the reference point and the current point, we use bigger size circles with different colors. Yes, we need to use dual axis with circles. The following formula is applied to identify the two points and assign bigger size to them:
We can use Size editor to fine tune the actual size of the circle.

For the coloring, we use a lightly different formula to create a dimension:
Then we assign appropriate colors to 1, 2 and 3.

Reset the reference point with a reset button

After we are done with the business, we should not leave the reference point remain highlighted  Thus we created a reset button sheet for resetting the highlighted reference point. First, we need to create 3 values for the 3 reference attributes to be reset with.
For example, the Rest Date is 1/1/1900. The Reset Sales is reset to 0. The Reset Sub Category is None. 
We need 3 parameter actions from the reset button sheet to reset the 3 attributes.
De-select the reference point and the reset button

In a Tableau dashboard, when we select/click a data mark, such as a reference point or the reset button in our case, it will stay selected until we click somewhere else. This is not good for us because we may not click anywhere soon. So we will apply a de-select action right away to the sheet in question. 
We need to create two fields with True and False each as values. And place them in the Details of the sheets in question. 
Here is the de-select filter action for the reset button:

There you go. It is not a complex dashboard in principle. We just have quite a few steps to get it done. It's a good exercise for playing with parameter actions.

Feel free to download the companion workbook and play with it. Leave comment below or contact me at twitter @aleksoft if you have questions.
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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.

(Addendum: Jonathan Drummey has a much better Tableau-only solution that I missed from his presentation. I only caught later part of the presentation. You might ask him about it if you know him.)

In a recent presentation, Tableau visionary HOF Jonathan Drummey talked about a solution for a variable row heights in a text table. The question apparently came from a perfectionist tableau designer. Tableau is not really made for text processing.

[Forward: I asked ChatGPT o1-mini who then wrote this. Hope it helps. All the credit and the blame go to ChatGPT.

I went over the plan and it looked decent. Whether it can be done in 30 days or not, it depends on the person and the time he spends on it. By the way, ChatGPT can be a really good study buddy. Ask it questions whenever you have any.]

This comprehensive 30-day plan is designed to take you from a Tableau beginner to an advanced user.

Mundane charts are those basic ones that all data visualization beginners can create, possibly with Show Me in Tableau. They are the boring ones at times because many people tend to create fancier ones just to show off. 

I actually like the mundane ones a lot because they are not only easy to create but also easy to be read by the stakeholders.

Pareto chart is a very powerful tool, providing great insights into the data set and into the business at stake.

A while ago, Sharon came to me asking a question regarding Pareto Chart Multiples. That is, per each category, there is a Pareto chart. And we need to create Pareto charts for all the categories. This chart allows us to quickly view the few most important factors that matter to the majority of output in each category. 

Vilfredo Pareto (1848-1923) is the father of the 80/20 rule: 80% of output are produced by 20% of input. It works magically well through all the years.

[Update: The product manager Wilson Po alerted me that the Viz Extension is still a work in progress. It will not be part of the incoming version 2024.1. Instead, it will be released later in 2024. Just be patient]

Tableau 2024.1 is coming. I got a chance to test drive it. As I wrote a bunch of posts on Sankey chart tutorials in the past, I am most excited by the new Sankey chart type. Here I would like to share what I learnt. This is a quick preview. Your comments are welcome.

Buzzfeed recently asked Midjourney to draw images of people in 50 US states.  So the AI drawing tool created 50 images of couples that represent its perception of the people in each state.

I just put the images into a tiled map in Tableau. Each image is added as a background in each tile.

And also I added Viz-in-tooltips to enlarge an image to look at more details.

Feel free to download the workbook and explore it.
1

The folks at Business Expert had a brilliant idea. They asked AI's perception on UK banks as a dog. I am inspired to do the same on US banks.

ChatGPT is asked to confess its perceptions on top US banks as a dog. Then Midjourney is tasked to generate the images. Check out what dog is matched to your favorite bank.

All are put together into a single-sheet Tableau dashboard. Feel free to check it out.

Through my previous post on the new Sankey chart type, I got in touch with Wilson, the product manager leading the development of this new chart type. I made some comments on creating multi-level Sankey via cascading of single Sankey's. He told me it can be done already by dropping more dimensions into the Level card.

As an enthusiastic user of Sankey charts, I am excited to learn that a Sankey chart type is being piloted in Tableau Public (Web Edit only). I wrote about Sankey chart design in multiple posts. Sankey chart may appear in different forms depending on applications. 

I played a little with it just to evaluate it. Here are my initial findings and comments.

1. The basic Sankey

I can quickly create a Sankey with 2 dimensions and 1 measure.
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