using nchoosek to gather possible combinations of data

Hi there ,

I am trying to use 'nchoosek' for the data that i have that contains 15 sets of x,y,z coordinates. I want to find all possible pairs of coordinates (x,y and z) data as described in my script.

This is the code I have but I am not sure how to correct my code so I get 105 combinations and not 14190 x 3 which is what the nchoosek function is currently giving me.

As you can see I initially had my x,y,z in seperate vectors but didn'ty know how to use the function with all 3 data. I then tried making a matrix which the function rejected. I finally made the 'dat' vector by combining all the x,y,z vctors into one.

In my script nchoosek is told to take 3 at a time because the order of the 'dat' vector is x1 co-ordinate, y1 co-ordinate, z1 co-ordinate ... xn co-ordinate, yn co-ordinate, zn co-ordinate.

Any help would be much appreciated !!

% script to caluclate the correlation dimension of points 

% with delta[log N_D (R)] / delta (log R) ( taken from Kagan.Y (2007)
% Earthquake spacial distribution: The correlation dimension. 
% here 
% D = dimensionality = 3-D 
% N = total number of earthquake pairs = n(n-1)/2
% R = distance between points = sqrt((x2-x1)^2 + (y2-y1)^2 + (z2-z1)^2)

N = 15*(15-1)/2 %the number of pairs I can have 

% The Data set (15 points) 
x_vals=[-9.33203	-9.92969	-9.40234	-9.47266	-8.83984	-9.50781	-10.0703	-9.08594	-9.50781	-10.0352	-9.12109	-9.05078	-9.26172	-9.82422	-10.3516];
y_vals=[27.8633	27.6172	27.6523	27.5117	27.9336	27.6172	27.3359	27.6172	27.6172	27.2305	27.9336	28.0039	27.793	27.7227	26.7734];
z_vals=[10.0098	8.04297	8.97461	7.98086	9.51289	8.04297	10.1133	10.0305	7.96016	7.98086	9.47148	7.77383	8.76758	9.34727	7.79453];


dat=[-9.33203		27.8633		10.0098 -9.92969		27.6172     8.04297 -9.40234		27.6523		8.97461 -9.47266		27.5117		7.98086 -8.83984		27.9336		9.51289 -9.50781		27.6172		8.04297 -10.0703		27.3359		10.1133 -9.08594		27.6172		10.0305 -9.50781		27.6172     7.96016 -10.0352		27.2305		7.98086 -9.12109		27.9336		9.47148 -9.05078		28.0039		7.77383 -9.26172		27.793		8.76758 -9.82422		27.7227		9.34727 -10.3516		26.7734     7.79453]

k=nchoosek(dat,3)

[KSSV]

YOu have already asked this question and a discussion is going on there.......without closing the existing question it is not fair to open a new question which is as same as your previous question.

Answer 1

[KSSV]

N = length(x) ; 
idx = nchoosek(1:N,2) ; 
xi = x(idx) ; yi = y(idx) ; zi = z(idx) ;