Linear Regression in Log Scaled Plot

[daoriaf]

My data is non linear but becomes linear when log transformed. To keep the axis values easy to understand, I have a plot of the untransformed data with the axis in the logarithmic scale.

I want to plot a linear regression line on the same plot but I cant get it to look linear because my plot if of the untransformed data. Is there any way I can do it?

Thanks!

 

[RickXL]

My data is non linear but becomes linear when log transformed. To keep the axis values easy to understand, I have a plot of the untransformed data with the axis in the logarithmic scale.

I want to plot a linear regression line on the same plot but I cant get it to look linear because my plot if of the untransformed data. Is there any way I can do it?

Thanks!

I have just tried in Excel 2010 and it is possible to choose Logarithmic when adding a trend line. Does that not work for you?

I drew the scatter plot, right clicked the line, selected Add Trendline then selected the Logarithmic option.

 

[daoriaf]

That won't work because it would give me a natural logarithmic regression (Ln). I need it to be a LOG10 regression.

 

[RickXL]

It seems to work for both for me.

 

[daoriaf]

It seems to work for both for me.

How do you get the logarithmic regression option to do LOG10 and not LN?

 

[RickXL]

Nothing.

I have not checked this in detail but I will tell you what I have done and then you can judge if I am doing it right or not.

I listed some numbers from 1 to 35. I took ln of those numbers and plotted them with a logarithmic x-axis and fitted a logarithmic trend line. The result was a straight line graph.

When you queried my initial answer I changed the calculation to log10 and repeated. I still got a straight line graph.

 

[pgc01]

Hi

It is always better to post a table with data.

Can you post a small table with sample data? This way we can all do the same test.

Also, which axis has the log scale?

 

[pgc01]

When you queried my initial answer I changed the calculation to log10 and repeated. I still got a straight line graph.

Logarithms of numbers to different bases differ only by a constant scale factor.

 

[RickXL]

Logarithms of numbers to different bases differ only by a constant scale factor.

That's right: logB(x) = logD(x)/logD(B). NB logD(B) is a constant.