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kemelmi1 (73) 37 Articles, 36 Replies, 73 Points

Since 5/19/2012 11:04:39 AM, kemelmi1 has written 37 articles and participated in 36 conversations.
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kemelmi1

kemelmi1's articles:
 Items(37) /4 Next >> Last >| making an evaluation of a VERY long expression much faster 8 28 (7/3/2009 12:10:24 PM) comp.soft-sys.matlabHello, How can an evaluation of a very very long expression can be made faster. My expression has terms with the operation .* between matrices and then those terms are summed together for example: A.*B + B.*C...kem spatial finite differences in two dimensions (something like 2 21 (2/20/2009 10:48:25 AM) comp.soft-sys.math.mathematicaHi, Is there a possibility in mathematica to get the coefficients or formula for approximation of spatial derivatives with finite differences. And, to get these formulas also for different orders of appro...kem a simple question about EulerEquations 0 30 (2/4/2009 10:33:40 AM) comp.soft-sys.math.mathematicaHi, It seems that mathematica gives a different expression for Euler- Lagrange equation. Isn't the answer to: EulerEquations[ f[u'[x],u[x],x] , u[x] , x] should be: Derivative[0, 1, 0][f][Deriv...kem simplifying a resulted derivative expression 2 24 (2/3/2009 12:17:16 PM) comp.soft-sys.math.mathematicaHi, I have a function f[ux, uy, vx, vy, wx, wy, u, v, w, x, y] I am doing different manipulations with this function and the results I get have expressions like that: Derivative[0, 0, 0, 0, 0, 0, 1, 0, 0...kem remove higher orders terms from mathemtica's result 2 118 (7/29/2008 10:10:33 AM) comp.soft-sys.math.mathematicaHi, Given this: K = (1+vy) (zx+wx) + vx (zy+wy); Expand[K^2] Is it possible to remove automatically the 3rd and 4th orders from the result of 'Expand[K^2]' ? By 3rd order I mean terms like: 2 wy z...kem what regularization is used in slash operator on sparse rank deficient matrices? 5 26 (5/12/2008 12:53:38 PM) comp.soft-sys.matlabHi I use slash to solve the system A x =b and my A is sparse rank deficient matrix. Do you know what kind of regularization is used by matlab? Tikhonov regularization? Thanks ...kem need explanation: something that works with \ operator doesnt work with lsqnonlin function 0 26 (5/5/2008 6:34:29 PM) comp.soft-sys.matlabHi, I have a LINEAR problem that I can solve using \ (slash) operator. I need to solve a NON_LINEAR version of this problem. For this I suppose I should use LSQNONLIN. I tried to use it and it doesn't...kem what is better to use: fmincon OR lsqnonlin 1 146 (5/5/2008 6:21:46 PM) comp.soft-sys.matlabHi, My objective function is to minimize the L2 norm of some vector + I have a linear constraint on the variables. So the output of the objfun: 1) in case of using lsqnonlin: F = [ f_1 ; f_2 ; ...kem maximum number of variables to be used with fminunc,lsqnonlin 6 69 (5/1/2008 11:25:54 AM) comp.soft-sys.matlabHi, What is the maximum number of variables that can be used with fminunc or lsqnonlin functions? In my case these get out of memory for 6000 variables. Does it make sense? Can this be optimized some...kem nonlinear optimization 1 37 (4/30/2008 3:36:53 PM) comp.soft-sys.matlabHi, I am trying to solve the following problem using matlab's optimization toolbox. ----------------------------------------------------------------- The problem is: min_z || A(:) - S(:)||^2 ...kem

kemelmi1's replies:
 Items(21) /3 Next >> Last >| PBRT: spot lights 3 6 (7/3/2006 4:32:20 AM) comp.graphics.algorithmsHello, This is a question about PBRT, in case someone can help me I will reaslly appreciate it. I created a cone, and I need to illuminate it using spot/point light source. I doesn't really work for me, I on...kemelmi1 (73) ezsurf 1 22 (9/10/2007 6:15:51 AM) comp.soft-sys.matlabHi, To show implicit surfaces I am using 'ezsurf' e.g. ezsurf('x^2+y^2') Now I need to plot only one contour of this surface, e.g. x^2+y^2=5 How can I do that? Thanks ...kemelmi1 (73) invert 'imtransform ' 2 45 (12/5/2007 5:09:32 PM) comp.soft-sys.matlabHi, How can I invert the operation of imtransform. e.g. im1 = imtransform(im,TFORM,'XData',[1 w],'YData',[1 h]); .....some processing.... now I want to make: im2 = imtransform( *im1*, *TFORM_inverse* ,'XD...kemelmi1 (73) using Dsolve for equation: y'' + |y|^2y=ay 3 43 (12/20/2007 9:52:19 PM) comp.soft-sys.math.mathematicaHi, Is it possible to use DSolve to solve the equation: y'' + |y|^2 y=ay ? DSolve[y''[x] + Abs[y[x]]^2 y[x] - a y[x] == 0, y[x], x] gives some strange solution with symbols like K\$1764^2 thanks...kemelmi1 (73) the fastest way to find whether sparse large matrix is singular/rank deficient 9 20 (4/15/2008 11:30:34 AM) comp.soft-sys.matlabHi, What will be the fastest way to find out whether a given matrix (sparse, large,non-square) is singular or rank deficient. I am using svds(A'A,1,0) to get the smallest singular value for now, bu...kemelmi1 (73) Defining the elements of a Matrix 1 45 (4/30/2008 10:40:36 AM) comp.soft-sys.matlabHi, Is there a way that I can define the element index (row, column) of a matrix. For example I have the following matrix in descending order a = [50,30,10,1], and I've located the highest value using...Rasha (11) nonlinear optimization 1 37 (4/30/2008 3:36:53 PM) comp.soft-sys.matlabHi, I am trying to solve the following problem using matlab's optimization toolbox. ----------------------------------------------------------------- The problem is: min_z || A(:) - S(:)||^2 ...kemelmi1 (73) maximum number of variables to be used with fminunc,lsqnonlin 6 69 (5/1/2008 11:25:54 AM) comp.soft-sys.matlabHi, What is the maximum number of variables that can be used with fminunc or lsqnonlin functions? In my case these get out of memory for 6000 variables. Does it make sense? Can this be optimized some...kemelmi1 (73) what regularization is used in slash operator on sparse rank deficient matrices? 5 26 (5/12/2008 12:53:38 PM) comp.soft-sys.matlabHi I use slash to solve the system A x =b and my A is sparse rank deficient matrix. Do you know what kind of regularization is used by matlab? Tikhonov regularization? Thanks ...kemelmi1 (73) making an evaluation of a VERY long expression much faster 8 28 (7/3/2009 12:10:24 PM) comp.soft-sys.matlabHello, How can an evaluation of a very very long expression can be made faster. My expression has terms with the operation .* between matrices and then those terms are summed together for example: A.*B + B.*C...kemelmi1 (73)