1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Working out the equation for coordinates on a graph

  1. Mar 6, 2017 #1
    I have a series of data points for X and Y points on a graph. The data is quite random and I am trying to work out a trend line so I can then form an equation for the line. How would I go about working out the equation for the data below.
    (0, 580)
    (6.7, 495)
    (13.4, 445)
    (18.7, 365)
    (22.8, 350)
    (27, 340)
    upload_2017-3-6_20-7-31.png
     
  2. jcsd
  3. Mar 6, 2017 #2

    DrClaude

    User Avatar

    Staff: Mentor

    Unless there is an underlying model that would suggest otherwise, I would consider that to be a straight line and do a linear least-square fit.
     
  4. Mar 6, 2017 #3
    I'm not sure how I can apply that to the data that I have. Where would I start with working out an equation?
     
  5. Mar 6, 2017 #4

    DrClaude

    User Avatar

    Staff: Mentor

    You need to first calculate the averages, ##\bar{x}## and ##\bar{y}##. Then use eqs. (16) and (20) in the link I gave you to get ##\mathrm{ss}_{xx}## and ##\mathrm{ss}_{xy}##. You then get the slope from eq. (27) and the intercept from eq. (28).
     
  6. Mar 7, 2017 #5
    I was expecting to get a trend line that looked like an exponential curve. Is it possible to work out an equation that would give me an exponential curve?
     
  7. Mar 7, 2017 #6

    DrClaude

    User Avatar

    Staff: Mentor

    The problem with the non-linear case is that you can't get a direct answer. It becomes a multidimensional minimization problem.

    The best is to use existing software to do this. Most graphing programs can do this, as well as other software such as Matlab.
     
  8. Mar 7, 2017 #7
    Ok, thanks. I have the Matlab software, but am unsure how to programme my data.
     
  9. Mar 7, 2017 #8

    DrClaude

    User Avatar

    Staff: Mentor

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Working out the equation for coordinates on a graph
  1. Equation of a graph (Replies: 4)

Loading...