k-Wave

1. KHO
   

   Member
   Joined: Nov '12
   Posts: 11

   Hi all,

   I was wondering, in what order the recorded data is actually stored. For a sensor that is built up from a list of cartesian coordinates, this is pretty clear (the data is stored in the same order as the sensor locations are defined), but for a sensor that is defined as a binary mask there is multiple options for the order of the sensor data.

   For example, if the plane x = a serves as a sensor, will the sensor data be stored in order of increasing y and then increasing z (i.e. grid(a,1,1), grid(a,2,1), grid(a,3,1), ..., grid(a,1,2), grid(a,2,2), ...) or vice versa (i.e. grid(a,1,1), grid(a,1,2), ..., grid(a,2,1), grid(a,2,2), ...), or maybe a totally different order?

   Posted 12 years ago #

2. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Hi KHO,

   The ordering follows the MATLAB column-wise linear indexing (i.e., the order the matrix elements are physically stored in memory and on disk). In 3D, this means the matrices are indexed first in the x-direction (dimension 1), then the y-direction (dimension 2), and then the z-direction (dimension 3). Thus for your example, (a plane x = a), the order would be grid(a, 1, 1), grid(a, 2, 1), etc.

   One way to visualise the matrix ordering is to use reshape:

   >> Nx = 4; Ny = 3; Nz = 2;
   >> reshape((1:Nx*Ny*Nz), Nx, Ny, Nz)
   
   ans(:,:,1) =
   
        1     5     9
        2     6    10
        3     7    11
        4     8    12
   
   ans(:,:,2) =
   
       13    17    21
       14    18    22
       15    19    23
       16    20    24

   Hope that helps,

   Brad.

   Posted 12 years ago #

3. KHO
   

   Member
   Joined: Nov '12
   Posts: 11

   Ah yes, that makes perfect sense.

   Thank you very much!

   Posted 12 years ago #

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