By adjusting a few axis format variables in Excel, we can simply plot a log-log graph. Both axes in the log-log or natural log-log graph are really on a logarithmic scale. Similar to the equation **y = c. x**** ^{a}**, this graph illustrates whether the variables are in a constant power relationship. In this case, the X and Y are related by a power of ‘a’ as in the image below.

- The line should have a smaller curve if a dataset derived from this equation is shown using a logarithmic scale.

### Step 1 – Create a Logarithmic Graph by Using the Charts Tool of Excel

- Select the
**Scatter Chart**from the**Charts**group under the**Insert tab**.

- A blank chart will appear.
**Right-click**on the chart and choose the command**Select data**from the context menu.

- A new window titled
**Select Data Source**will appear. Click the**Add**command icon in that window.

- Choose the range of cells that we will use as data for the X-axis and the Y-axis in the following window.
- Choose the cell address that currently has the cells and cell name in it to insert the title there.

- Click
**OK**.

- Right-click on the labels for the Horizontal Axis to generate the logarithmic graph.
- Select
**Format Axis**from the context menu.

- It will reveal a new side panel. Select the
**Logarithmic scale**checkbox and enter**Base 2.7**under the**Axis**Options in the**Format Axis**side panel. - Set
**Vertical****Axis Crosses**to**Automatic**as well.

- Similar to the y-axis, check the Logarithmic scale checkbox for the x-axis under the Axis Options in the
**Format Axis**side panel.

**Read More: How to Calculate Slope and Intercept in Excel**

### Step 2 – Find the Slope of the Logarithmic Graph

We have data that could fit the theoretical **y = c. x**** ^{a}** curve. The slope of a natural log-log plot is equal to the exponent

**a**‘s value, which is calculated as

`a=ln(y2)-ln(y1)/ln(x2)-ln(x1)`

- Select
**Add Trendline**to find the equation of our data like the image below.

- Select Exponential as the trendline like in the following image.

- Select
**Display Equation on Chart**in the**Trendline Options**.

`y = 12.484e`

^{0.7387x}- We will get the following equation to find the slope in each point of our x-value for this example the x-values are
**Day**.

`dy/dx=12.484 x 0.7387 x e`

^{0.7387x}- Using the differential equation, we will get the slope in Excel like the following image.

The formula is as follows:

`=12.484*0.7387*EXP(0.7387*B5)`

- Drag the fill handle down to complete the series.

**Read More: How to Find the Slope of a Line in Excel**

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