Excel graph with 3 variables in 2D

microsoft excel

We've conducted a hydrogen peroxide experiment (conversion to water and oxygen) under the effect of catalase in 5 different pH levels. We noted the volume of the formed oxygen after 30 seconds and 60 seconds.

Our problem is that we have 3 variables: pH, time, volume of created O2.

Does anyone have any idea how to successfully graph using excel?

Best Answer

First, I would absolutely stay away from the 3d chart options. There's too many reasons to list here, but this blog post by Jon Peltier is worth a good place to start.

You have three relatively good options for charting three variables, but you'll need to play with your data to determine whats best for the story you're trying to tell.

  1. Bubble charts use the basic layout of an XY or Scatter Chart, but allow you to encode a third variable in the data point's size. This builds in a problem similar to Pie Charts in the difficulty of interpreting and comparing the relative areas of circles.

  2. Scatter Charts can be used similar to a Bubble Chart, but with multiple series or data points encoded by color or shape. This is probably better for categorical data.

  3. Panel Charts may be your best option. Create a series of Scatter Charts that are identical (in scale and formating), but only vary based upon one of your variables (e.g. pH). Present these in an array and they'll allow for easy comparison.

EDIT: After considering the description of your data more, I don't think a Bubble Chart is a good option. You appear to have 5 data series (for each pH level), each with two values (30 and 60 seconds). Either option 2 or 3 above are still good, or you could consider a Bump Chart (can be created as a Line Chart in Excel). If you can provide a sample of data, it would be easy to demonstrate a couple of these options.

EDIT2: After a bit more consideration, since your data is only 10 points, I would go with a regular Scatter Chart. Since you don't have interval measurements between 30 and 60 seconds, I don't think a line would be appropriate, since it would imply those values. Instead, just plot and label your 10 points. Here's a sample of what it could look like:


EDIT3: Chart data revised based upon Jon Peltier's suggestion.


And, to round things out, a bump chart.


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