How to Create a Semi-Log Graph in Excel

A semi-log graph is a type of graph that uses a logarithmic scale on the y-axis and a linear scale on the x-axis.

This type of graph is often used when the values for the y variable have much greater variability compared to the values for the x variable.

This occurs often in datasets in finance, economics, biology, and astronomy among other fields.

The following step-by-step example shows how to create a semi-log graph in Excel for a given dataset.

Step 1: Enter the Data

First, let’s enter the values for a fake dataset:

Step 2: Create a Scatterplot

Next, highlight the data values:

Along the top ribbon, click Insert. Then click the first option under the Scatter graph option:

The following scatterplot will automatically be displayed:

From the plot we can see that the values for the y variable have much higher variability than the values for the x variable.

This means it’s a good idea to convert the y-axis into a logarithmic scale to visualize the y-values more effectively.

Step 3: Modify the Y-Axis Scale

Next, right click the y-axis. In the dropdown menu that appears, click Format Axis:

In the window that appears on the right side of the screen, check the box next to Logarithmic scale:

The y-axis will automatically be converted to a logarithmic scale:

The x-axis remains on a linear scale, but the y-axis has been converted into a logarithmic scale.

Notice how much easier it is to interpret the y values in this graph compared to the previous graph.

Additional Resources

How to Create a Log-Log Plot in Excel
How to Transform Data in Excel (Log, Square Root, Cube Root)
How to Perform a Box-Cox Transformation in Excel

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