Unable to understand SNR equation in Matlab
To express power $P$ in $\mathrm{dB}$ one performs this operation:

$$P_{\mathrm{dB}}=10\log_{10}(P)$$

The inverse operation would then be

$$\frac{P_{\mathrm{dB}}}{10}=\log_{10}(P) \implies 10^{\frac{P_{\mathrm{dB}}}{10}}=P$$

And that's exactly what you are doing in that MATLAB equation (i.e. expressing the SNR in linear scale from the data in decibels).

Note that the .^ means that the operation is being carried out element-wise.