Finding the slope of a section of a graph in excel

[member 392791]

Hello,

I have a graph of a tensile test of a metal sample, and I wish to find the slope on the graph of only the elastic region of the graph, meaning of the entire graph, there is only one section of it that I am interested in finding the slope for.

Is there a way in excel to make it such that you only find the slope of certain data points, as opposed to the slope of the entire graph?

Thank you

 

[Ibix]

I can only suggest a few hacks. I assume your elastic data is in B2:B10, and the plastic in B11:B15.

Option 1. Copy B10 into C10 and move B11:B15 into C11:C15. Plot both lines on the same chart using the same colours and point styles, and fit the elastic line. Hide the legend to conceal the implementation.

Option 2. Delete the plastic data; plot and fit the elastic data in the normal way, making sure to dispaf the equation of the line. Note down the equation, delete the chart and put the plastic data back in. Use the equation to create a column C containing the fit line and plot in the normal way.

Option 3. Do a least-squares fit yourself and plot it in the nomal way. I think Excel has SUMSQ and SUMPRODUCT functions that may prove useful in determining the parameters.