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