Question

I am not an expert on R or really good at statistic so I will be brief.

I am using R to get the Distance Matrix of a matrix shown below the way it appears on R.

When I apply dist(matrix) I see the following:

          1         2         3         4         5         6
2 16.155494                                                  
3  5.830952 15.329710                                        
4  2.236068 18.055470  6.244998                              
5  7.681146 13.928388  9.110434  8.124038                    
6  8.306624 11.489125  9.110434  9.273618  2.449490          
7 11.090537 10.392305 12.124356 12.247449  5.099020  3.464102

So my questions are three, first, is that result ok?, second, why the calculation has less rows than we had before?, and finally why There are more Columns than at the beginning?

Answer 1

I get the same result. (Whether this is ‘correct’ might depend on your goals. Your last question suggests to me that you do not understand that these are distances between the rows.) The length of the object returned is always the number of columns in combn(n,2) and combn(7,2))==21 in this case, where n= number of rows. It is displayed as a lower triangular matrix of dimension (n-1)x(n-1). There is no row #1 simply because the distance from a row to itself is zero and printing it would not be useful. There will also be n-1 columns where n is the number of rows, regardless of the number of original columns. The number of columns only determines the dimension of the space in which the distances are being calculated.