How to create and interpret a Scatterplot in Google Sheets

Whenever I’ve taught data analysis classes or data visualization classes, for General Assembly or privately or online, I find that the humble scatterplot is often poorly understood.

Perhaps it’s because they’re less common than simple bar charts, line charts or pie charts? Or maybe it’s because they take a bit more mental effort to understand what they’re telling us?

Regardless, they’re a crucial tool for analyzing data, so it’s important to master them. This post looks at the meaning of scatterplots and how to create them in Google Sheets.

What is a scatterplot?

Simply put, a scatterplot is a chart which uses coordinates to show values in a 2-dimensional space.

In other words, there are two variables which are represented by the x- and y-axes.

scatterplot in google sheets

In this example, the scatterplot shows the relationship between pageviews of a website and the number of signups that website received. As you can see, when the number of pageviews increases, the number of signups tends to also increase. They are positively correlated, but more on that in a minute.

Often the variable along the x-axis is the independent variable, which is the variable under the control of the experimenter, and the variable up the y-axis is called the dependent variable, or measured variable, because it’s the variable being observed to see how it changes when the independent variable changes.

It’s possible for both variables to be independent, in which case it doesn’t matter which axis they’re plotted on and the scatterplot shows any correlation between the two.

If you’ve enjoyed this post, check out my upcoming Data Analysis in Google Sheets course, which covers how to conduct data analysis and statistical calculations in Google Sheets. Check out the syllabus here >>

Why is it useful?

A scatterplot is incredibly useful because it can show you, at a glance, what the big picture is, what the overall relationship is, what the trend is, between two variables.

Looking at the numbers alone is not particularly intuitive. It’s hard, impossible often, to determine how they’re related to each other.

Scatterplot example

Let’s take a look at a real-world example, using data showing property sales in Manhattan. I’ve extracted the data for properties between 1,000 sq.ft. and 5,000 sq.ft. and removed any without a sales price listed.

This leaves 250 values in a dataset, like so:

Scatterplot data

To create a scatterplot, highlight both columns of data (including the header row).

Then click Insert > Chart

Initially it’ll create a terrible bar chart, where each of the 250 rows of data is represented by a bar. Yikes!

bad bar chart

It’s a very simple fix to transform it into a scatterplot. On the chart menu, on the Data tab, simply choose the Scatter option, as shown in this image:

scatterplot menu

There you have a nice scatterplot!

Focus on a single point for a moment (shown in red in this image):

Reading a scatterplot

You can read off a pair of values, in this case 3,000 sq. ft. and $3,750,000, which tell us that we have a data point (representing a property sold in Manhattan) which was 3,000 square foot and had a sales price of $3.75 million.

We can write it as a coordinate pair: (3,000 , 3,750,000)

So each point, each plot, in our chart represents a coordinate pair of area and sales price, each plotted according to the rows of data in our dataset.

This is the real power and beauty of a scatterplot. It shows all of those rows of data in a single chart, so we can absorb something about the dataset as a whole.

Interpreting a scatterplot (correlation)

Well all those points on your scatterplot are pretty and they show something, but what exactly? And is there anything else we can glean from the scatterplot?

They show trends within our dataset.

But it’s hard to see this from just the points, so we can add a trendline like so (shown in red):

scatterplot with trendline

Ah ha! That’s interesting and useful.

It shows a general upward trend, which is what we’d expect. As the size of a property increases, so does it’s sales price.

Now, if we want to predict a sales price for a given area, say 4,500 sq. ft., we can use this line.

Start at the 4,500 sq. ft. mark on the x-axis, trace up to the line and then across to the y-axis and read off the value:

scatterplot and trendline

I can read off a value of $5,900,000 as the predicted value of a 4,500 sq. ft. property.

You might be wondering how to do that a bit more “scientifically”?

Well, we can use the equation of the trend line to calculate the number.

The line equation takes the basic form:

y = ax + b

So to predict y, we need to know the value of x (4,500 sq.ft. in our example) multiplied by the value of a (which is the slope of the line) and adding on the value of b (the intercept, or where the line crosses the y-axis).

We calculate a from our data using the SLOPE function:

=SLOPE( B2:B277 , A2:A277 )

which gives us: 1166.42218

We calculate b from our data using the INTERCEPT function:

=INTERCEPT( B2:B277 , A2:A277 )

which gives us: 712264.7317

Then I can calculate my predicted y-value using the equation:

y = 1166.42218 x + 712264.7317

into which I plug in the x-value of 4,500 sq. ft.:

y = 1166.42218 * 4500 + 712264.7317

to get the answer: $5,961,165

All that from a humble scatterplot.

How do we know if this line is a good fit? Will it give us “good” predictions?

Stay tuned for the next post, where we’ll look at how to answer that question.

Want to learn more about Data Analysis?

There’s a lot more to scatterplots, and my upcoming Data Analysis in Google Sheets course will do a deep dive into scatterplots and how to use them to understand your data better.

If you’ve enjoyed this post, check out my upcoming Data Analysis in Google Sheets course, which covers how to conduct data analysis and statistical calculations in Google Sheets. Check out the syllabus here >>

What the world’s richest man can teach us about averages

This is a story about a bar, 10 regular folks and the world’s richest man. Somewhere along the way, we’ll seek to demonstrate the robustness of the different average measures, but more on that in a minute.

I want you to picture your favourite bar or pub.

For me, it might be a pint of ale at The Dickens Inn, near the River Thames in London:

Dickens Inn London pub

I should just finish this blog post here, and we could all spend the rest of the day in happy reverie, supping our favourite tipple.

Alas, that won’t do! We have work to do and things to learn, so let’s get started.

The dataset

Imagine ten friends, all regular folks, sitting at the bar, eating and drinking, chatting and laughing. A most convivial scene. The beer tastes delicious of course, the floor is dappled with sunlight and the comforting aroma of Pie & Mash wafts by their nostrils. Anyway, I digress.

Let us play a little game. Our subjects don’t mind because they’re fictional.

We ask them all to write down their salaries in our Google Sheet, so we have the following results:

Ten salary values

Good. That’s our dataset.

Calculating the averages

Continue reading What the world’s richest man can teach us about averages

Checkboxes (☑️) are now available in Google Sheets! Here’s three ways you can use them.

Checkboxes are now available in Google Sheets!

They give you a visual way to toggle between boolean values (true and false) in a spreadsheet cell. This opens up all sorts of opportunities to make your Sheets more interactive.

Adding a checkbox

You’ll find checkboxes under the Insert menu:

Insert checkboxes menu

At the moment they have a NEW label next to them, but that disappears after a while.

FALSE status

When you add a checkbox, it will show up in the cell or range of cells that you have highlighted, and it will be unchecked. If you look in the formula bar, the cell has a value of FALSE.

This means you can link to this checkbox cell with any formula, for example an IF statement, and it will behave as a FALSE value (when it’s unchecked).

False checkboxes

TRUE status

When you click on the checkbox itself, it will become checked (shown by a tick mark and grey background) and the cell value will change to TRUE. Again, you can use this in your formulas.

true checkboxes

Advanced Checkbox Options

Continue reading Checkboxes (☑️) are now available in Google Sheets! Here’s three ways you can use them.

Slow Google Sheets? 🐢
Here are 27 ideas to try today

Slow Google Sheets?

We’ve all been there, stuck watching the little loading bar creep slowly, frustratingly to it’s conclusion:

Slow Google Sheets loading bar

How can you speed up a slow Google Sheet?

First off, this is a difficult question to answer because there are so many factors that may or may not be causing you to have a slow Google Sheet.

What follows in this article is some suggested optimization strategies and some research into what causes slow Google Sheets.

Strategies to speed up Google Sheets

  1. How to recognize slow Google Sheets (details)
  2. Know the size limits of Google Sheets (details)
  3. Measure a Google Sheet’s size (details)
  4. Measure a Google Sheet’s calculation speed (details)
  5. Delete un-used cells (details)
  6. Convert formulas to static values wherever possible (details)
  7. Use closed range references (details)
  8. Remove volatile functions or use with caution (details)
  9. Vlookup strategies (details)
  10. Index-Match strategies (details)
  11. Query function strategies (details)
  12. Array Formula strategies (details)
  13. Import Formula strategies (details)
  14. Google Finance function strategies (details)
  15. Use IF statements to manage formula calls (details)
  16. Manage expensive formulas with a control switch (details)
  17. Use Filter, Unique and Array_Constrain functions to create smaller helper tables (details)
  18. Avoid long calculation chains (details)
  19. Reference data on the same Sheet (details)
  20. Use helper columns (details)
  21. Split your slow Google Sheet into separate Sheets (details)
  22. Use Conditional Formatting sparingly (details)
  23. Leverage the power of Apps Script (details)
  24. Use custom formulas sparingly (details)
  25. Other troubleshooting tips for slow Google Sheets (details)
  26. Understand changes in the cloud can take time to propagate (details)
  27. Know when it’s time to move to a database (details)

Continue reading Slow Google Sheets? 🐢
Here are 27 ideas to try today

Explaining syntax differences in your formulas due to your Google Sheets location

Did you know that formulas are written differently depending on where in the world you’re located? For example, the syntax in the US is different to that in Italy.

This post explores the syntax differences that occur based on your Google Sheets location, i.e. the location you’re working in, assuming your Google settings match (which they would by default).

Formula syntax based on Google Sheets location
What wizardry is this? Either this format will look utterly normal to you, or it won’t.

If you’ve ever copied a template but been unable to get it working, or simply not understood a formula, then it’s possible you’ve run into this syntax issue due to Google Sheets location.

This handy guide will show you the differences and hopefully help you translate seamlessly when sharing Sheets in different locations.

For the most of the world, aside from Europe, you write decimals with a decimal point notation (for example $2.50) and your formulas will use commas to separate the different parts.

I’m currently based in the US, my Google account is set to a US location, so all the articles and template downloads on this site use this notation. (Incidentally, I’m from the UK originally, but since they use the same decimal notation there, formulas in my Google Sheets are the same regardless.)

For countries using decimal comma separators (for example €2,50), which is most of the European countries and a select few others, the syntax for formulas is slightly different, as explained below.

So, ask yourself now where you’re based and how you write your decimal numbers, and then see the different sections below for guidance on how your formulas are written.

How to change Google Sheets location

Before getting to the nitty-gritty of formula syntax, let’s first see where we set the location.
Continue reading Explaining syntax differences in your formulas due to your Google Sheets location