Bivariate Gaussian distribution of the Gaussianised HRS data: K-band versus 250 μm data. Red symbols correspond to late-type galaxies, black ones to early-type. Upper limits are identified as downward triangles. Here, z = G^-1(u) with G^-1(u) the inverse function of the standard Gaussian CDF, and u is the uniform random variable from the CDF of the LF at the given frequency (see text).