Spherical mean (source code)

= Spherical mean
{title2=$M_rf(x)$}
{wiki}

The spherical mean of a function on $\mathbb R^n$ is its average over a sphere:
$$
M_rf(x)=\frac1{|S^{n-1}|}\int_{S^{n-1}}f(x+r\omega)\,d\omega.
$$