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!

Catmull Rom splines, scaling the input.

  1. Jan 20, 2010 #1
    Hi. I've tried doing some camull-rom interpolation for the following data.
    x y
    0.2 1.221402861
    0.3 1.349864712
    0.4 1.491929555
    0.5 1.649697833
    0.6 1.828165418
    0.7 2.042000232
    0.8 2.332915111
    0.9 2.808281551
    1 3.718281828
    1.1 5.597908484
    1.2 9.511853345
    1.3 17.45514585
    1.4 32.98066546
    1.5 62.14672813
    1.6 114.9041952
    1.7 207.0733374
    1.8 363.0963701
    1.9 619.7925202
    2 1031.389056

    I chose to interpolate for point 1.1 (i'm assuming this point is non-existent).
    I am using the following method:

    f(x) = [1, x, x^2, x^3] * M * [p0, p1, p2, p3]

    And M is the matrix,

    0.0 1.0 0.0 1.0
    -0.5 0.0 0.5 0.0
    1.0 -2.5 2.0 -0.5
    -0.5 1.5 -1.5 0.5

    The "tension" value (greek letter tau) is 0.5.

    Thus, the 4 points chosen were 0.9, 1, (2 before 1.1), 1.2, 1.3 (the 2 after 1.1).

    I did it in matlab and got wrong values (using an input of 1.1 and expecting to get a value close to 5.5979). I have since learnt that the input needs to be between 0 and 1. How do I scale this value of 1.1 to be between 0 and 1 ? And does anything else change , in the M matrix, matrix of points [p0, p1, p2, p3] ?

    Thankyou.
     
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted



Loading...
Similar Threads for Catmull splines scaling Date
Derivatives of B-splines Oct 20, 2015
Restricted (Natural) cubic spline - wrong equation? Apr 30, 2015
What Is A "Cubic" Spline? Feb 23, 2015
B-Spline (Another Method) Jan 10, 2015