• The 1R algorithm (One Rule or OneR), is to select a single rule. Although this may seem overly simplistic, it tends to perform better than you might expect.• As demonstrated in empirical studies, the accuracy of this algorithm can approach that of much more sophisticated algorithms for many real-world tasks.• The way this algorithm works is simple.• For each feature, 1R divides the data into groups based onsimilar values of the feature.• Then, for each segment, the algorithm predicts the majority class.• The error rate for the rule based on each feature is calculated and the rule with the fewest errors is chosen as the one rule.