JoannesPaulus said:you cannot "read" the SNDR from a picture. You need to integrate the power of the noise (including harmonics, for SNDR) over the band (Nyquist, in this case). Then you divide the integrated signal power by the integrated noise plus distortion.
JoannesPaulus said:I do not think you really can... of course you could estimate the power in a small set of bins but it would just be a guess.
A graph like the one you show is mostly used to show the level of harmonics and SFDR but you cannot really "calculate" anything else.