A method for generating stimulus response curves (e.g., dose response curves) shows how the phenotype of one or more cells change in response to varying levels of the stimulus. Each "point" on the curve represents quantitative phenotype for cell(s) at a particular level of stimulus (e.g., dose of a therapeutic). The quantitative phenotypes are multivariate phenotypic representations of the cell(s). They include various features of the cell(s) obtained by image analysis. Such features often include basic parameters obtained from images (e.g., cell shape, nucleus area, Golgi texture) and/or biological characterizations derived from the basic parameters (e.g., cell cycle state, mitotic index, etc.). The stimulus response curves may be compared to allow classification of stimuli and identify subtle differences in related stimuli. To facilitate the comparison, it may be desirable to present the response curves in a principal component space.