Correction to: Nature Machine Intelligence https://doi.org/10.1038/s42256-021-00306-1, published online 12 April 2021.

In the version of this Article originally published, in the caption of Fig. 2 the expression \(\left| {\theta - \theta } \right|_{\mathrm{F}}^2/{\mathrm{max}}\left( {\left| \theta \right|_{\mathrm{F}}^2,\left| \theta \right|_{\mathrm{F}}^2} \right)\) was incorrect; it should have been \(\left| {{\mathbf{\uptheta }} - \theta } \right|_{\mathrm{F}}^2/{\mathrm{max}}\left( {\left| \theta \right|_{\mathrm{F}}^2,\left| {\mathbf{\uptheta }} \right|_{\mathrm{F}}^2} \right)\). In addition, a number of Greek letters were missing or incorrectly formatted in the PDF version of the Article, while the HTML version was correct. This has been corrected.