Finding index location in volume?

For instance, I have

x = 2000:0.5:2004; y = 45000:0.3:45009; z = 10:0.2:12;

which are axes of a volume, x has length of 9, y has 31 and z has 11.

Now a volume filled of nan values and given by;

C = rand(9,31,11)*nan;

I want to fill this volume with values when new values come up, it will have x, y, z and the corresponding value. So, I need to find the closest index location and fill the value there. E.g.

x =2002.13, y = 45006.811, z = 11.36 have value of 10000 so i want to fill the corresponding C(x,y,z) = 10000;

here I need to find the index for x = 2002, y = 45006.9, z = 11.4 and fill the value 10000 there in C.

how can I use the values converted to closed index in the volume. Thanks

Answer 1

[Andrei Bobrov]

x = 2000:0.5:2004; 
y = 45000:0.3:45009; 
z = 10:0.2:12;

x0 = 2002.13;
y0 = 45006.811;
z0 = 11.36;

C = nan(9,31,11);
C0 = 1000;

[~,ii] = min(abs(x - x0));
[~,jj] = min(abs(y - y0));
[~,k]  = min(abs(z - z0));
C(ii,jj,k) = C0;

[Syed Abdul Salam]

work perfectly. Thanks

Answer 2

[Nicolas B.]

Hi,

for your case, I would write your code like that:

 x = 2000:0.5:2004; y = 45000:0.3:45009; z = 10:0.2:12;
 % no need to use rand() to generate a table of NaN and it's more flexible with automatic size
 C = NaN(length(x), length(y), length(z));
 
 % your points
 pts = [2002.13, 45006.811, 11.36];
 
 % your coordinates
 [~, xc] = min(abs(x - pts(1)));
 [~, yc] = min(abs(y - pts(2)));
 [~, zc] = min(abs(z - pts(3)));
 
 % your value
 C(xc, yc, zc) = my_value;
 

Do it help you?

[Syed Abdul Salam]

Yes, thank you. Both works perfectly.