Flashcards in Data selection and manipulation Deck (16)

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1

## which.max(x)

### returns the index of the greatest element of x

2

## which.min(x)

### returns the index of the smallest element of x

3

## rev(x)

### reverses the elements of x

4

## sort(x)

###
sorts the elements of x in increasing order; to sort in decreasing

order: rev(sort(x))

5

## cut(x,breaks)

###
divides x into intervals (factors); breaks is the number

of cut intervals or a vector of cut points

6

## match(x, y)

###
returns a vector of the same length than x with the elements

of x which are in y (NA otherwise)

7

## which(x == a)

###
returns a vector of the indices of x if the comparison op-

eration is true (TRUE), in this example the values of i for which x[i] == a (the argument of this function must be a variable of mode logi- cal)

8

## choose(n, k)

### computes the combinations of k events among n repetitions = n!/[(n − k)!k!]

9

## na.omit(x)

### suppresses the observations with missing data (NA) (sup- presses the corresponding line if x is a matrix or a data frame)

10

## na.fail(x)

### returns an error message if x contains at least one NA

11

## unique(x)

### if x is a vector or a data frame, returns a similar object but with the duplicate elements suppressed

12

## table(x)

### returns a table with the numbers of the differents values of x (typically for integers or factors)

13

## subset(x, ...)

### returns a selection of x with respect to criteria (..., typically comparisons: x$V1 < 10); if x is a data frame, the option select gives the variables to be kept or dropped using a minus sign

14

## sample(x, size)

### resample randomly and without replacement size ele- ments in the vector x, the option replace = TRUE allows to resample with replacement

15

## prop.table(x,margin=)

### table entries as fraction of marginal table

16