rho_f: Calculates the uncumulated rho_f-estimates
In myllym/marksummary: Calculate summary functions for marked point patterns

Calculates the uncumulated rho_f-estimates

1	rho_f(mark1, mark2, bin_idx, weight_m, mtf_func_l, mtf_name, n_bin)

`mark1`	The marks of the first points of pairs in a vector.
`mark2`	The marks of the second points of pairs in a vector.
`bin_idx`	A vector of indices which tell which radius bin each point pair belongs to.
`weight_m`	A weight matrix for point pairs.
`mtf_func_l`	A list of mark test functions all of which take two real marks and return a real value.
`mtf_name`	The names of the mark test functions. Matches mtf_func_l in order.
`n_bin`	The number of bins in the radius vector.