Truncated log10 transform.
x : num | num iterable
values to be transformed.
th : num
values below th are transormed to 0. Must be positive.
r : num (default = 10**4)
maximal transformed value.
d : num (default = log10(2**18))
log10 of maximal possible measured value. tlog(10**d) = r
Array of transformed values. :