Data Structure: Vector
A list common functions in R for working with vector objects:
1. Creating Vectors
c()– Combine values into a vector.seq()– Generate a sequence of numbers.rep()– Repeat elements to form a vector.
2. Accessing and Modifying Vectors
length()– Get the length of a vector.[]– Subset elements of a vector.append()– Append elements to a vector.unique()– Extract unique elements from a vector.sort()– Sort elements of a vector.rev()– Reverse elements of a vector.which()– Find indices of elements that meet a condition.
3. Vector Math and Operations
sum()– Sum of vector elements.mean()– Calculate the mean.median()– Calculate the median.sd()– Calculate the standard deviation.var()– Calculate the variance.min()/max()– Find the minimum/maximum value.range()– Get the range (min and max).diff()– Lagged differences of vector elements.prod()– Product of elements.
4. Logical and Conditional Functions
any()– Check if any elements areTRUE.all()– Check if all elements areTRUE.is.na()– Check forNAvalues in the vector.na.omit()– RemoveNAvalues from the vector.ifelse()– Vectorized conditional statements.
5. Applying Functions to Vectors
sapply()– Apply a function to each element and simplify the result.vapply()– Similar tosapply()but allows specifying output type.
6. Character Vector Functions
paste()/paste0()– Concatenate elements.tolower()/toupper()– Convert to lowercase or uppercase.nchar()– Count characters in elements.substr()– Extract or replace substrings.
7. Set Operations
union()– Union of two vectors.intersect()– Intersection of two vectors.setdiff()– Elements in one vector but not the other.%in%– Check if elements are in another vector.
8. Other Useful Functions
sample()– Randomly sample elements from a vector.match()– Find positions of first matches in a vector.table()– Frequency table of vector elements.cut()– Divide a continuous vector into intervals.