ENH: More features for ReceptiveField

• support score method for use with GridSearchCV
• use custom Ridge solver for speed and multiple regularization types (i.e., Ross’s Fourier-based code)
• change to positive lags for causal behavior #4550
• backward transform
• Add CUDA support for the fitting
• if necessary, make tmin/tmax/sfreq logic consistent with Epochs class
• forward/backward model tutorial?
• plot method that is smart enough to at least deal with 1D (STA) and 2D (STRF) plotting, probably using NonUniformImage class rather than pcolormesh
• decimation (decimate data before fitting or model after fitting?)
• refactor with linear_regression_raw, XDawn (categorical data, #4940)

[rkmaddox]

+1 for positive lags. If you think of the TRF (no S) when a stimulus is a bunch of clicks (so, x = click train, y = EEG signal), then the brain response should be at positive lags, because a click causes the brain signal to wobble after the click happens.

I agree that it gets a little hairier with the STRF, but positive lags still make by far the most sense to me.

[larsoner]

If the current code issues Ridge, the auto and cross covariances need to be recalculated, so it will add time. With TDR (or a custom Ridge) where these are stored I doubt it will add much time