Manipulating Data

• Randomizing order
• - Numeric vectors, Character vectors, and Factors
• Comparing vectors or factors with NA
• Mapping vector values - Change all instances of value to value y in a vector

• Re-computing the levels of factor

• Renaming columns in a data frame
• Merging data frames
• - Search for duplicate or unique rows across multiple data frames.
• Re-computing the levels of all factor columns in a data frame

• Summarizing data - Collapse a data frame on one or more variables to find mean, count, standard deviation, standard error of the mean, and confidence intervals
• - Data frames with individual cases, data frames with counts, and contingency tables

• Calculating a moving average
• - Convert a sequence into blocks of a given length and average within each block.
• Filling in NAs with last non-NA value