Rank: 351 based on 253 downloads (last 30 days) and 7 files submitted
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Per Sundqvist

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Company/University
Chalmers Tekniska Högskola

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Professional Interests:
quantum and mathematical physics

 

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Files Posted by Per View all
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  • 7
Updated   File Tags Downloads
(last 30 days) 		Comments Rating
09 Jan 2009 Screenshot Exponential fit, without start-guess Fits 1) f=s1+s2*exp(-t/s3) or 2) f=s1+s2*exp(-t/s3)+s4*exp(-t/s5) to numerics, without startguess Author: Per Sundqvist exponential, nonlinear, noise, fit, least square, exact 71 9
  • 3.5
3.5 | 7 ratings
12 Nov 2008 3D Data Interpolation 3D interpolation using modified 4-point vector Newton interpolation Author: Per Sundqvist mathematics, nonuniform, 3d interpolation, interpolation, newton, approximation 61 5
  • 2.5
2.5 | 6 ratings
16 Jan 2008 Screenshot erfi function Imaginary error function (could be complex) using matlab's incomplete gamma function gammainc Author: Per Sundqvist complex, imaginary error funct..., gaussian, integral 33 0
13 Jan 2005 Orthogonal Linear Regression Fits a line y=p0+p1*y to a dataset (xdata,ydata) in an orthogonal way. Author: Per Sundqvist interpolation, linear regression, interpolation orthogo..., least squares fit, approximation 24 10
  • 3.0
3.0 | 8 ratings
22 Nov 2004 Screenshot Points Inside polygone Finds those points (xi,yi) who are inside the polygon, defined by the vectors (x,y) Author: Per Sundqvist interpolation, 2d contour, polygon, find, random, approximation 8 3
  • 2.0
2.0 | 2 ratings
Comments and Ratings by Per
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  • 1
Updated File Comments Rating
03 Nov 2008 Exponential fit, without start-guess Fits 1) f=s1+s2*exp(-t/s3) or 2) f=s1+s2*exp(-t/s3)+s4*exp(-t/s5) to numerics, without startguess Author: Per Sundqvist

HI, B. Roossien. I'm not sure what kind of help you want. The code is standard but assumes perhaps that you are a bit familiar with matlab. nargin<4 means that your input arguments are 3 and you will then get options as specified, later on, at the end of the program used in the matlab function lsqcurvefit. Maby I should tell that t and f should be vectors of the same size? Or do you want me to explain the theoretical model? Its lengthy though...

As well I realize now that I in the beginning of the program should have wrote:
t=t(:);
f=f(:);
[t,ix]=sort(t);
f=f(ix);
%to make time and function f vectors sorted column vectors in case they have a funny formate like matrices.
/Per

Comments and Ratings on Per's Files View all
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Updated File Comment by Comments Rating
14 Feb 2010 Exponential fit, without start-guess Fits 1) f=s1+s2*exp(-t/s3) or 2) f=s1+s2*exp(-t/s3)+s4*exp(-t/s5) to numerics, without startguess Author: Per Sundqvist Judd, Gordon

This is just the fit I have been looking for, but I find I get poor fits on experimental data (y positions of oscillating cantilever beam) depending on the time limits used in the data.

Is there any constraint requiring that an integer number of vibration cycles be included in the limits for the time data? I get a reasonably good fit for 1 cycle but a poor fit when several cycles are included.
15 Jun 2009 Exponential fit, without start-guess Fits 1) f=s1+s2*exp(-t/s3) or 2) f=s1+s2*exp(-t/s3)+s4*exp(-t/s5) to numerics, without startguess Author: Per Sundqvist Pholchai, Nitipat

Works fine. Can you also please include any reference for the theory/method you used in this code? that should be helpful for any practitioner.

02 Jun 2009 Cylinder Between 2 Points Generalization of the MATLAB function cylinder Author: Per Sundqvist Wardrop, Glen

Lovely - worked first time, saved me hours of work
17 May 2009 Cylinder Between 2 Points Generalization of the MATLAB function cylinder Author: Per Sundqvist Edmond, Kazem

It's great. Thanks so much.
23 Mar 2009 Exponential fit, without start-guess Fits 1) f=s1+s2*exp(-t/s3) or 2) f=s1+s2*exp(-t/s3)+s4*exp(-t/s5) to numerics, without startguess Author: Per Sundqvist Bozovic, Gavrilo

The intent is good, but the code is very messy, which made that, after getting initially bad results, I didn't even try to check where the error came from.
Top Tags Applied by Per
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approximation, interpolation, 2d contour, 3d interpolation, complex
Files Tagged by Per View all
  • 1 - 5 of
  • 7
Updated   File Tags Downloads
(last 30 days) 		Comments Rating
09 Jan 2009 Screenshot Exponential fit, without start-guess Fits 1) f=s1+s2*exp(-t/s3) or 2) f=s1+s2*exp(-t/s3)+s4*exp(-t/s5) to numerics, without startguess Author: Per Sundqvist exponential, nonlinear, noise, fit, least square, exact 71 9
  • 3.5
3.5 | 7 ratings
12 Nov 2008 3D Data Interpolation 3D interpolation using modified 4-point vector Newton interpolation Author: Per Sundqvist mathematics, nonuniform, 3d interpolation, interpolation, newton, approximation 61 5
  • 2.5
2.5 | 6 ratings
16 Jan 2008 Screenshot erfi function Imaginary error function (could be complex) using matlab's incomplete gamma function gammainc Author: Per Sundqvist complex, imaginary error funct..., gaussian, integral 33 0
13 Jan 2005 Orthogonal Linear Regression Fits a line y=p0+p1*y to a dataset (xdata,ydata) in an orthogonal way. Author: Per Sundqvist interpolation, linear regression, interpolation orthogo..., least squares fit, approximation 24 10
  • 3.0
3.0 | 8 ratings
22 Nov 2004 Screenshot Points Inside polygone Finds those points (xi,yi) who are inside the polygon, defined by the vectors (x,y) Author: Per Sundqvist interpolation, 2d contour, polygon, find, random, approximation 8 3
  • 2.0
2.0 | 2 ratings
 

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