```Date: Feb 6, 2013 8:36 AM
Author: Jos
Subject: Re: access matrix

"amira ali" wrote in message <kert0i\$qr8\$1@newscl01ah.mathworks.com>...> "Jos (10584)" wrote in message <kerqnq\$hg3\$1@newscl01ah.mathworks.com>...> > "amira ali" wrote in message <kerejb\$qqn\$1@newscl01ah.mathworks.com>...> > > "Jos (10584)" wrote in message <keqi7l\$934\$1@newscl01ah.mathworks.com>...> > > > "amira ali" wrote in message <keohlb\$51a\$1@newscl01ah.mathworks.com>...> > > > > need help urgently> > > > > > > > > > i have location of interest points in matrix A(2*13 ) where 2 is x,y of point and 13 is total number of points for example:> > > > > x                                  y> > > > > 72.6781959551728	46.7543453323974> > > > > 71.9155271184922	100.930596158669> > > > > > > > > > and i have another matrix called flow  (120*160) this matrix contain velocity of every pixel  (v in x direction) and (v in y direction). all i need it how can i get the velocity of 13 interest points from this matrix flow so finally i must have> > > > > x         y                 v(x)          v(y)> > > > > 72.	46.7543        0.087396	-0.135287> > > > > > > > Using x and y as indexes in a matrix requires them to be integers ...> > > > > > > > Your question is also not very clear. You have "another matrix called flow" which is 2D but you index a one-dimensional vector v, using v(x) and v(y).> > > > > > > > Please rephrase ...> > > > > > > > ~ Jos> > > > > > it's not one dimensional vector it  will be 13 rows and 4 coulmns , i written one row as example (location of points and their velocities)> > > > > > in matlab v(x) means "the value of v at position (=index) x".> > > > Perhaps you can give a very brief example of what you want to achieve with two points (= two x and y values) and a flow matrix which is, let's say, 3 by 4? It would be very helpful if you show the exact inputs and desired outputs.> 1-i have img1 (120*160*3) and img2 (120*160*3) then i get optical flow between two images in matrix called  flow (120*160*2) (matrix flow contain velocity of every pixel in x direction and y direction).> > 2- i apply sift detector  the image represent flow form img1 to img2 (mean flow image)> and i get location of set of interest points  13*2(13 point s  and 2 is cordinates of point)> > 3- i want to get velocity of this points  from matrix flow> > simply that clear the meaning of optical flow which i read it> > pixel at the coordinates p = (x; y) in an image I. If the pixel moves by u; v pixels between time t - 1 and time t, the brightness constancy assumption can be formulated as:> I(p; t - 1) = I(x + u; y + v; t)Dear Amira,I think I'm beginning to understand your question, and my answer would be the same as Bruno'sIn order to help you further I strongly suggest you do provide: "a very brief example of what you want to achieve with two points (= two x and y values) and a flow matrix which is, let's say, 3 by 4? It would be very helpful if you show the exact inputs and desired outputs."as mentioned before.And, please refrain from using multiple question marks etc, if you want to be taken seriously.~ Jos
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