3

I I have an Excel scatter chart with x and y values. I set the logarithmic scale in x-axis and y-axis.

When I add a linear trend line to the graph, the line is not linear but appears like a curve.

How can I make a linear trend line on a logarithmic-scaled chart?

Sample data:

x:
18449
22829
25395
36869
101419
125498
208144
2001508
14359478
17301785

y:
269,09
273,89
239,50
239,50
175,13
176,73
151,94
135,15
131,55
121,55
2
  • convert x,y values to logarithmic scale to some table and plot/regress the converted data
    – Spektre
    Aug 19 '14 at 12:50
  • 1
    @pnuts You should post that as an answer so the question can be resolved.
    – Excellll
    Aug 20 '14 at 15:27
2

Adding a Power Trendline seems to have worked. tusham has kindly saved me the trouble of explaining why:

The power trendline is given by y=c*x^b. Believe it or not, you can use LINEST to calculate the parameters. Here's how.

Take the log of the above equation to get ln(y)=ln(c)+b*ln(x). This is a linear equation!

and

A log-log display of the data doesn't change the underlying analysis. If you plot a bunch of X,Y pairs and ask for a power trendline, you will get the same result irrespective of whether the plot shows either or both of the axes on a log scale.

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