# How can I calculate incremental growth rate using a logarithm regression analysis? I have count data from 1992-2022 of a species and want to calculate the growth rate on a 3 year moving average.

I want to calculate the mean compound annual growth rate using a three-year sliding average to consider the average 3 calving intervals of species and subsequent cohort structured calving cycles.

I hconducted a linear regression using the natural log in SPSS. What is the best way to look at the growth rate for each 3-year time block, eg. 1992-1994, 1993-1995....2020-2022? I am using the same data and similar methodology as a previous study (mine is an update from 2016) so it has been suggested I follow my co-investigators method, however she is currently unavailable and I need to get onto analysing the data for write up. A previous paper with a brief data analysis methodology and figure is attached. I just cannot decipher how they came up with the values in the figure.

Is anyone able to help with insight? and soem simple instructions to follow (I am not familiar with stats)

"Data analysis: The mean compound annual growth rate was calculated using a three-year sliding average to consider the average 3 calving intervals of SRWs and subsequent cohort structured calving cycles. A simple exponential regression was fitted to the long-term count data and presented with 95% confidence intervals and standard deviation."

This description is taken from PhD thesis chapter which was submitted for publication (minus this text) and the link is attached below. Figure is on page 677 which I want to replicate.
2022 paper DOI accessed here

I can also send data.

• Kav10

Low bounty!

• Kav10

Which figure are you referring to?

• Kav10

• Bridget

Attached is the paper with Figure 4 teh one I want to replicate. I can complete myself, but just need some help figuring out the process. I think it should be fairly straighforward fbut for some reason just can't wrap my brain around it. In that case I may have under estimated how much time it would take to help figure out.

• Kav10

Creating a box chart of the data using regression analysis should be straight forward. I can give you general guidance on doing that.

• Kav10

Thanks for attaching the paper.

• Bridget

Okay perfect and this can be done for each 3 year time block?

• Kav10

Yes, you can calculate 3-year moving average.

• Bridget

I am using SPSS also do you know if that can be done?

• Kav10

I can give you instructions to create the box plot in Excel.

• Bridget

That would be amazing thank you

• Daniel90

The offered bounty is too low for the amount of time and energy one needs to spend to answer this question!

• Bridget

Bounty increased

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• Bridget

Thank you Kav10