converting XYZ file to GRID

Hello all,

I am trying to convert a XYZ file, i.e.

X Y Z 1.5e3 2.8e6 2 2.5e3 3.8e6 2.1 . . .

into a grid, that would be several matrix for the X, Y and Z values

If I do it with my first file, it works, but if I try with the second one, it does not work properly the function unique creates more values than actually it has for the X and Y matrix, so when I create my Z matrix, there is no enough values...

load = XYZ ('points.xyz');
c=0;
x=unique(XYZ(:,1));
y=unique(XYZ(:,2));
[X,Y] = meshgrid(x,y);

for j=1:758
for i=1:3153
c=c+1;
Z(j,i)=XYZ(c,3);
end;
end;

Does someone know what is wrong? The files are: With this works: https://dl.dropboxusercontent.com/u/22755010/points%20working.dat

With this does not work: https://dl.dropboxusercontent.com/u/22755010/points%20no%20working.xyz Thanks in advance

Javier

Answer 1

[Walter Roberson]

http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F

[Javier Abanades]

I do not follow you

[Walter Roberson]

if you are getting more values than you expect then possibly the problem is with values that look the same when displayed but are just slightly different. unique is going to notice the slight difference and treat them as different values.

Answer 2

[Javier Abanades]

My problem is that the unique function generates a regular grid and I just want to generate a grid in the points where I have data, beacuse if it generates a regular grid I do not have Z values for every point...

How can I solve it?

[Walter Roberson]

Suppose, in the 2D case, you had data points like this:

@
@
@@@

with the @ showing where the points were defined. How would you convert that into a grid and yet only generate the grid for the points where you had data?

[Javier Abanades]

I know it is a bit strange but I have an xyz file with thousands of points... so I would like to transform that matrix (2e6,3) into 3 matrix where I can save the values of X, Y and Z respectively.

Instead of one matrix of (2e6,3) having 3 matrix of (1e3, 2e3) where I save X, Y and Z values

[Walter Roberson]

At present, your 2e6 x 3 matrix is indexed at (point number, dimension number), where point number is 1 : number of points and the points are not ordered with respect to each other. Dimension number would be 1 for X, 2 for Y, 3 for Z.

After the transform, you want three 2D matrices, one each for X, Y, Z. But what are the indices for those 2D matrices? (1e3 by 2e3) would have the same number of entries as 1e6 x 1 would have, but what is the 1 : 1e3 intended to represent, and what is the 1 : 2e3 to represent?

Answer 3

[Chad Greene]

I wrote a function for this called xyz2grid.

[Mike Stin]

Hello, I'm completely new here. I have XYZ data in an excelsheet or a text document and would like to edit this data with your script to create a 3d chart interface in Excel.

For this purpose the data must be available in mesh/grid form

However, I am not familiar with Matlab and could use some help.