I measured the Received Signal Strength in dBm between a receiver $R_x$ and a transmitter $T_x$ at different distances $d_1, d_2, \dots, d_n$, and all the values that I obtained are (of course) negative (e.g. $[-80;-30]$dBm.
Now I want to try to fit the Rice/Rician distribution (to compute the PDF) on every single distance (I don't know how can I fit on all distances), but I understood that I cannot do this with negative values.
What can I do? I don't think that convert to mW is the right choice, since I guess that I can lose a lot of information about it.
Update
I converted the measurements in mW, but when I try to fit the Rician distribution on a single distance in Matlab I receive an error like this:
z = [1.06814447885193e-05;6.15885529115340e-07;5.92324913934610e-07;5.78868610067183e-07;4.76244529410218e-07;6.17419014199609e-07;5.88870773232456e-07;6.07952991784579e-07;5.45833265534826e-07;5.10093747291922e-07;5.65405462521790e-07;5.77032135332931e-07;5.71965719059118e-07;6.27480161997852e-07;6.85756606121613e-07;6.10435806184937e-07;6.36253229871620e-07;6.05326936425641e-07;5.91057864030903e-07;6.83266298400135e-07;7.08842910309525e-07;5.86111172475547e-07;5.74129681879599e-07;5.71715543837535e-07;5.75638721577247e-07;5.52408051608360e-07;6.42598932860734e-07;6.98441441500089e-07;6.60419670228017e-07;6.90907647790195e-07;7.09447070946132e-07;6.79719923717695e-07;6.01229110180695e-07;6.15077725903605e-07;6.11730310782606e-07;6.35096910397487e-07;6.70301204806594e-07;5.65340371559323e-07;6.80675313427682e-07;5.89915761635370e-07;7.49290109458934e-07;7.13444180817969e-07;6.56387043686654e-07;5.48908555607045e-07;6.94368482631736e-07;7.06463941494969e-07;6.51163426781562e-07;6.13493548436490e-07;5.95223405098983e-07;6.30245857770948e-07];
pd = fitdist(z,'Rician')
The parameter S must be a nonnegative finite numeric scalar.