UPDATE: As of R2020a, the sinr function now supports returning output values when provided transmitter site inputs:
ORIGINAL ANSWER:
When passed transmitter sites, the sinr function performs visualization only and does not support an output argument. However in R2019a a new syntax was added to sinr that supports output values calculated at specified receiver sites:
In order to get the SINR values corresponding to the visualization, you could create an array of receiver sites and pass them as the first input. As an example of creating a grid of sites, see the Planning Radar Network Coverage over Terrain example where meshgrid is used to generate a grid of latitude/longitude coordinates.
