Rank: 762 based on 91 downloads (last 30 days) and 3 files submitted
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Christophe Lauwerys

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Files Posted by Christophe View all
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14 Aug 2011 Screenshot N-dimensionally spaced points Multidimensional extension and generalisation of LINSPACE and LOGSPACE. Author: Christophe Lauwerys linspace logspace mul... 2 0
21 May 2007 Datetickzoom - automatically update dateticks Label axis with date ticks that automatically update when zooming or panning Author: Christophe Lauwerys annotation, customization, date, time, zoom, pan 37 8
  • 4.71429
4.7 | 7 ratings
22 Mar 2006 PLOT4 Plot colored lines and points in 3-D space Author: Christophe Lauwerys 3d, 4d, data exploration, color, plot, graphics 52 3
  • 4.5
4.5 | 2 ratings
Comments and Ratings by Christophe View all
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02 Feb 2012 distance2curve Find the closest point on a (n-dimensional) curve to any given point or set of points Author: John D'Errico

As always, great submission, thanks.

Could one easily extend this algorithm to finding the closest point on a surface from given a point in space? Or from another given curve, surface, ... ?
13 Oct 2011 Random Vectors with Fixed Sum Randomly and uniformly generates vectors with a specified sum and values in a specified interval. Author: Roger Stafford

Nice. I'm trying to generate random data within a simplex defined by linear inequality constraints.

Lets say I already have the N vertices of the simplex defined by the inequalities. Is it then correct to first generate a random sample in the interval [0,1] with a sum equal to 1, and then take the inner product of this sample with the vector of vertices?

Something along the lines of:

X = rand(6,2);
k = convhull(X);
plot(X(k,1),X(k,2),'b'), hold on
nv = numel(k)-1; % Nmuber of vertices
X = X(k(1:end-1),:); % Remove repeated first vertex
L = randfixedsum(size(X,1),1000,1,0,1);
Y = L'*X;
plot(Y(:,1),Y(:,2),'r.'), hold off

Maybe I shouldn't trust my vision on this, but the samples don't really look uniformly spread within the simplex. For some reason they only seem to do for a triangle.

Any thoughts?

Thanks

Christophe
11 Aug 2011 Fractions Toolbox create and manipulate fractions (K+N/D) using exact arithmetic Author: Ben Petschel

Great stuff, but I wonder how your two statements quoted below can be unified.

In other words: how can you define for instance SIGN and ABS for objects that represent polynomials? Not to mention GCD for multivariate polynomials ... Not an expert but do you need Groebner bases for this?

Thanks

Christophe

A)

% Non-standard objects must include 0, 1, -1 and require the following
% operations to be defined in order to create a fraction object:
% gcd
% rem
% sign
% abs
% +, - , .*, ./
% ==, <, <=, >, >=, ~=
%
% The following additional operation definitions are recommended:
% *, .^
% sort
% floor
% factor
% gcd (3-output form)
% rat (if floor(x) or mod(x,1) is not always equal to x)

B) If there exists a suitably defined polynomial object, this toolbox could be used to perform partial fractions.
09 Aug 2011 Symbolic polynomials Object-oriented symbolic polynomial manipulation in one or more variables Author: Levente Hunyadi

sympolys x y
subs(x*y+1,'x',x-1)

returns

x*y + x - y - 1.000000

whereas

x*y - y + 1

is correct.

A bug?
02 Nov 2010 groebner manipulate and solve systems of multivariate polynomial equations by computing the groebner basis Author: Ben Petschel

Ben, thanks for your answer.

Could you have a look at another feature/bug:

P = str2poly({'x1*x2*x3'});

P{1}

ans =

     1 1 1 1

poly2str(P)
??? Index exceeds matrix dimensions.

Error in ==> poly2str at 68
          str = [str,varnames{k}]; % print variable name

Thanks

Christophe
Comments and Ratings on Christophe's Files View all
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07 Nov 2011 Datetickzoom - automatically update dateticks Label axis with date ticks that automatically update when zooming or panning Author: Christophe Lauwerys latheefth

Hi,

I need to zoom it to milli sec, but it happens only till second.
datetickzoom('x','HH:MM:SS.FFF');
Is there any way of doing it?
11 Jun 2011 Datetickzoom - automatically update dateticks Label axis with date ticks that automatically update when zooming or panning Author: Christophe Lauwerys Nicolas

hold arrowkey -> matlab crashes
24 Jun 2010 PLOT4 Plot colored lines and points in 3-D space Author: Christophe Lauwerys Christian

Hey! Got a problem.
I have created a [X,Y,Z]=meshgrid(x,y,z) for my computed data corresponding to the x,y,z. lets say we have c(x,y,z)=data in a loop.
No i wanna distinguish the data field into a stable data and unstable data. So I want to plot in one plot the data points with a value of less or equal 1. I thought about setting it NaN case 1 and the other way round. But got an error msg.

Help is very welcome.

Greetz Chris
21 Apr 2010 Datetickzoom - automatically update dateticks Label axis with date ticks that automatically update when zooming or panning Author: Christophe Lauwerys Karen
13 Jan 2010 Datetickzoom - automatically update dateticks Label axis with date ticks that automatically update when zooming or panning Author: Christophe Lauwerys Listmangof, Marc
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3d, 4d, annotation, color, customization
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(last 30 days) 		Comments Rating
14 Aug 2011 Screenshot N-dimensionally spaced points Multidimensional extension and generalisation of LINSPACE and LOGSPACE. Author: Christophe Lauwerys linspace logspace mul... 2 0
02 Nov 2010 groebner manipulate and solve systems of multivariate polynomial equations by computing the groebner basis Author: Ben Petschel groebner, polynomial equations 28 14
  • 4.66667
4.7 | 4 ratings
25 Jul 2008 Screenshot Find 'orphaned' m-files (in a directory tree) Author: Dimitri Shvorob depfun, orphan, files, directories, mgrep, rdir 4 1
21 May 2007 Datetickzoom - automatically update dateticks Label axis with date ticks that automatically update when zooming or panning Author: Christophe Lauwerys annotation, customization, date, time, zoom, pan 37 8
  • 4.71429
4.7 | 7 ratings
22 Mar 2006 PLOT4 Plot colored lines and points in 3-D space Author: Christophe Lauwerys 3d, 4d, data exploration, color, plot, graphics 52 3
  • 4.5
4.5 | 2 ratings

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