1. At a computing-device-based computing system, the computing-device-based computing system comprising one or more computing devices, each of the one or more computing devices comprising one or more processors, the computing-device-based computing system comprising one or more storage media, the one or more storage media having stored one or two data sets, a computing-system-implemented method for calculating simple linear regression coefficients for a modified computation set of a specified number of pairs of data elements of the one or two data sets, each of said pairs of data elements containing an observation of an independent variable and an observation of a dependent variable, the method comprising: initializing, by the computing-device-based computing system, a sum or a mean or both for each variable, and one or more components of simple linear regression coefficients other than a sum and a mean for a pre-modified computation set with a specified size n (n≥6) of one or two data sets on the one or more storage media; accessing, by the computing-device-based computing system, a pair of data elements to be removed from the pre-modified computation set and a pair of data elements to be added to the pre-modified computation set; modifying, by the computing-device-based computing system, the pre-modified computation set by removing the to be removed pair of data elements from the pre-modified computation set and adding the to-be-added pair of data elements to the pre-modified computation set; iteratively deriving, by the computing-device-based computing system, a sum or a mean or both for each variable in the modified computation set; directly iteratively deriving, by the computing-device-based computing system and based at least in part on the one or more components of simple linear regression coefficients other than a sum and a mean for the pre-modified computation set, one or more components of simple linear regression coefficients other than a sum and a mean for the modified computation set, wherein directly iteratively deriving includes: accessing the one or more components other than a sum and a mean without accessing all data elements in the modified computation set to reduce data accessing latency thereby saving computing resources and reducing the computing system's power consumption; and removing any contribution of the removed pair of data elements from each of the one or more accessed components mathematically and adding any contribution of the added pair of data elements to each of the one or more accessed components mathematically wherein not all data elements in the modified computation set are used during the directly iteratively deriving the one or more components to reduce number of operations performed by the computing system thereby increasing calculation efficiency; and generating, by the computing-device-based computing system and based on one or more of the derived components, simple linear regression coefficients for the modified computation set.