You've built your data logger and put your code on the board. You kept it in the bathroom while you showered and put it in the freezer for a bit to get some varied data. Now what do we do with that data? We make graphs!

Remove the SD card from your data logger, and use an SD card reader to plug it into your computer. You should have a file called "log.txt" on it. Copy that file to your computer.

Note that some spreadsheet programs require you to change the extension to ".csv". Otherwise they don't know what to look for and may import incorrectly.

Next, open the file into a spreadsheet program of your choice. We've used Google Sheets. Open a new spreadsheet.

Click File and choose Import.

At the top of the Import File window, click Upload. Then click "Select a file from your computer" and choose your log.txt file.

No changes are needed in the Import File dialog box - the defaults work for our project.

If the data imports with empty columns, you can delete the empty columns.

Now we have our data! It's almost ready to graph.

For Google Sheets, the Chart Legend feature behaves a little strangely. There's no way to edit it once it's in the chart. However, you do have the option to "Use row 1 as headers". So a workaround is to forgo the first data point and instead change it to a title that reflects the data below it. As the chart will be using column A for the x-axis, it is unnecessary to change the first data point in that column. In fact, it seems to mess with the ability to use row 1 as headers, so we recommend changing the data as you see in the image.

It's time to graph! Click the Insert Chart icon located towards the right side of the toolbar.

Tah dah! A graph!

But, it looks a little plain. So let's dress it up a bit.

Click on the graph, find the three-dots-menu in the upper right corner, and click "Edit chart", then choose "Customize".


Click on "Chart & axis titles" and enter a title for your graph.


Click on "Legend" and choose where you'd like your legend to be.

And that's it! Now you've got an amazing graph of your data! Now you can have fun seeing what happens to temperature and humidity when you move your project to different environments.

Here's the explanation of our data. We put our data logger in the freezer in the beginning. Humidity levels in the freezer are level for the most part but drop initially before leveling out. When it's removed from the freezer, any moisture in the air condenses on the sensor (and the rest of the data logger, so be careful!) and causes the humidity to reach 99%. Then as the sensor warms up and the condensation clears, both temperature and humidity level off.

Try putting it next to the heat or air conditioning duct, near your humidifier, in your fridge, in the bathroom while you shower, in an open window on a cold day or anywhere else you can think of to get fun variable data to work with! Have fun!

This guide was first published on Apr 30, 2018. It was last updated on Apr 30, 2018.
This page (Graphing Your Data) was last updated on Oct 21, 2020.