function averatio=radgrad(n)
%This function takes in an array of numbers of particles in four bins
%and calculates r*dc/dr based on the experimental observations of Karnis,
%Goldsmith & Mason.

%We have the concentrations:

ntotal=sum(n);
c=4*0.33*n/ntotal;

%We have the derivatives:

npt=length(c);
dcdr=(c(2:npt)-c(1:npt-1))/0.1;

%We have the radial mid points:
r=[.1,.2,.3];

%Thus we get the ratios:
ratio=r.*dcdr;

%and we return the mean:
averatio=mean(ratio);