Vector Functions
One of R's great strengths is its ability to evaluate functions over entire vectors, thereby avoiding the need for loops and subscripts. Important vector functions are listed in Table 2.2.
Table 2.2. Vector functions used in R.
| Operation | Meaning |
| max(x) | maximum value in x |
| min(x) | minimum value in x |
| sum(x) | total of all the values in x |
| mean(x) | arithmetic average of the values in x |
| median(x) | median value in x |
| range(x) | vector of min(x) and max(x) |
| var(x) | sample variance of x |
| cor(x,y) | correlation between vectors x and y |
| sort(x) | a sorted version of x |
| rank(x) | vector of the ranks of the values in x |
| order(x) | an integer vector containing the permutation to sort x into ascending order |
| quantile(x) | vector containing the minimum, lower quartile, median, upper quartile, and maximum of x |
| cumsum(x) | vector containing the sum of all of the elements up to that point |
| cumprod(x) | vector containing the product of all of the elements up to that point |
| cummax(x) | vector of non-decreasing numbers which are the cumulative maxima of the values in x up to that point |
| cummin(x) | vector of non-increasing numbers which are the cumulative minima of the values in x up to that point |
| pmax(x,y,z) | vector, of length equal to the longest of x, y or z, containing the maximum of x, y or z for the ith position in each |
| pmin(x,y,z) | vector, of length equal to the longest of x, y or z, containing the minimum of x, y or z for the ith position in each |
| colMeans(x) | column means ... |
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