For recipes using CTAB in seed solution, two competing morphologies are nanocubes and nanorods. Most cube recipes in the dataset utilize a consistent set of precursors, specifically without AgNO 3 . Our decision tree analysis identified the concentration of AgNO 3 as a fundamental factor (second decision point in Fig. ) separating rods and cubes. For the latter case without AgNO 3 , we found the opposite trend (third decision point) to one reported by Sau and Murphy, although we caveat that this was done with very few nanorod data points in this region. Sau and Murphy reported that lower CTAB resulted in the formation of nanocubes, as it promotes Au deposition on {111} faces and formation of {100} faces. Following this, Meena and Sulpizi have shown via molecular dynamics simulation that CTAB has higher packing density on Au(100) surfaces than on (111). This indicates the need for further exploration in the nanorod/nanocube formation in the absence of AgNO 3 . A synthesis (precursor) space with clearer decision boundaries from regularized logistic regression is shown in Fig. , showing 2D precursor space with multiple precursors. We utilized a learned matrix derived from multinomial logistic regression, with dimensions of 38 features by 4 morphology classes. To exemplify a low-dimensional space, we arbitrarily selected two rows from this matrix (corresponding to bipyramids and rods). This matrix (dimension of 38 by 2) was then multiplied with the design matrix with dimensions (434 samples, 38 features), revealing one of the low-dimensional spaces using the learned matrix.