Prediction of proliferation signal in combined dataset. A) A scatter plot of showing the correlation to the proliferation metagene for the combined dataset containing 793 ER+ breast cancer samples, with the histological grade colour coded where blue is grade 1, red is grade 3 and grey indicates either grade 2 or missing value. The correlation of this fit is indicated in the upper left corner. B) A histogram of correlations for the predictions for 500 permutations in which the combined dataset was randomly split into two and each half was used to predict the proliferation metagene of the other half. The lambda value was fixed at an optimal value of 120 based on a prior set of cross-validations.