Charts and Graphs

How to make stream graphs in Excel?

Last updated on July 16, 2020

Chandoo

Stream graph or stream plot is a variation of area chart that looks like a stream. Here is a quick demo of a stream chart. Learn how to create such a graph in this page.

Background & Inspiration

Stream graphs have been around for many years. But this particular graph, showing the appearance of X-men characters is originally designed by Cédric Scherer. I saw his tweet sometime back and immediately wanted to recreate this in Excel.

So I went to the github project page where Cedric shares his R code, datasets and detail on the construction for all his visuals. I grabbed a copy of the dataset and used it to make the interactive stream graph in Excel.

Big thanks to Cedric for the inspiration. 🙏

Download the Stream Chart Workbook

Please click here to download the Stream Chart: X-Men appearances workbook. Play with it to enjoy. Examine the calculations, worksheet setup and chart formatting options to learn more.

How to make a stream graph - 4 steps

As you can guess, there is no “Stream graph” option in insert ribbon on Excel. So we will need to make it by mixing a few bits and bobs. For the first part of the tutorial, let’s focus on creating a stream plot in Excel. The process involves 4 simple steps.

Make a regular area chart
Float the areas with a dummy series at bottom
Smoothen the areas
Format the chart

Let’s start with sample data as depicted below.

Step 1 - Make regular area chart

Select the data and insert a stacked area chart. We get this.

Step 2 - Float the areas with dummy series at bottom

To make our area chart look like a stream, we need to first lift the areas. To do this, we need to add a dummy series at the bottom.

But what would the value of this dummy series?

To make it look like a stream, each point of the area chart needs to move down or up around a center line.
We can do this by taking a big enough number (say 100) and subtracting half the height of total area at each point.
To make it look natural, we can add a small random number to this.

Here is how our dummy float series will look:

And this is how our area chart will look once you add the dummy series at the bottom.

Step 3 - Smoothen the areas

You must be thinking… “Hey, where is the stream… 😕?”

We are getting there. Our area chart has all sorts of sharp lines. We just need to smoothen it out. I recommend 60 grit sandpaper.

Just kidding. No need to sand the edges. We just use formulas to smoothen the data. Time for some concepts.

How to smoothen / curvify data in Excel?

If you are making a line graph, you can use the ever helpful “smooth line” option to smoothen it. Unfortunately, we need to use area charts for the stream effect. So we are out of luck and need to learn how to smoothen or curvify our data.

You can use regression to smoothen the data, but it tends to be too complex.

The easy option: use moving average.

Take your data and apply moving average with a window size of 5 (try few different options and pick the one that gives good looking curve).

Here is a tip on how to calculate moving average in Excel.

Here is the moving averaged data. Remember to include the dummy series in moving average calculations.

If you create an area chart from this data, suddenly those areas don’t look so sharp anymore. Our stream is almost ready!!!

Step 4 - Format the chart

This last step is real simple. Just format the chart by making dummy series transparent. Remove any unnecessary chart elements and you have a nice stream going.

Back to X-Men Appearances Stream Chart

Now that you know how to make a stream appear, let me unravel the rest of this beautiful x-men appearances chart.

Data for the visualization:

The data for this came from Github project page (link). It is in a convenient CSV format. I used Power Query to connect to the file and add an extra column to extract mutant character names.

Interactivity – Option buttons:

The interactivity in the stream graph is done with 4 option buttons, icons, text & conditional formatting. See below illustration to understand how they all create the illusion.

Stream chart edges – lines with smoothing option:

To get the crisp stream effect, I have added two lines, one at bottom and one on top of the stream. I made these lines smooth lines and colored them in white.

Axis labels are data labels on a hidden line:

I added another line series on top. Used that to make axis labels for important issue #s and hidden the line. We get these beauties.

Error bars for gridlines:

As regular gridlines can be too grainy, I removed them and used error bar technique to draw a line from bottom to top of the stream.

Legend is shapes + typed text:

The legend is almost manual. I just created a bunch of rectangles and typed the text in them. I used gradient fill technique to get two colors in the same box.

How did the stream tapered nicely?

That is for you to figure out. Use the download file to learn how that is done.

Stream Chart in Excel - Video

I made a video explaining the whole process. It has many additional charting tips too. Watch it below or on my YouTube channel.

Download Stream Chart Excel File

Just in case, you missed the link above…

Please click here to download the Stream Chart: X-Men appearances workbook. Play with it to enjoy. Examine the calculations, worksheet setup and chart formatting options to learn more.

Advanced Excel Charting Ideas & Inspiration

If you are looking for creative, fun and interesting ways to present data, you’ve come to the right place. Please click on below images to learn more.