Excel Graphs and Charts

Hi Jens

I tried to plot some of my data as an example to show you, but can't see any way that I can attach it to a forum post in the same way you did? Perhaps I don't have that permission?

I think we are on the right track, I just think my data and what I want to do is a little awkward, and maybe I am not describing it in the best way.

I have some raw data, which is a curved line, as well as some processed data which produces a line which is part curved, part linear.

I need to find the linear region of this "processed" data which corresponds to a particular curved region of the original "raw" data. Typically, I have been doing this visually by plotting the two data sets on the same graph, and then finding the correct range of x-values within which to calculate the partial regression line in the processed data set. This bit often requires a lot of manual adjustments to the line.


So the first part is - is there a way for me to get excel to identify the range of interest of x-values from the "raw" data, and use this range on the "processed" data and add the regression line to this part only.

Ideally, I'd like to do this from Excel plotting a chart so that I can visually see that everything is as it should be and the values are being extracted from the right part of the graph.


The second part is that I want to be able to extract the Gradient and Intercept values of that partial regression line so that they can be used in equations, and will recalculate automatically if I change the x-range, for example. At the moment I am having to type them in manually by copying them from the Equation, which I have displayed on the chart, and if I change the regression line slightly, I have to type the values in again so that the equations give the right results.



I hope this is clear, and please let me know if there is a way that I can send a file for you to see if that would help make it easier to understand? Equally, I'm not sure if Excel can necessarily do all of what I am asking it to in this case, but even if I can just extract the gradient and intercept values from the chart equation, that would be very helpful!

Thanks again!