R: Column and row-wise nth smallest value of a matrix/vector

Column and row-wise nth smallest value of a matrix/vector {Rfast} | R Documentation

## Column and row-wise nth smallest value of a matrix/vector

### Description

Column and row-wise nth smallest value of a matrix/vector.

### Usage

    colnth(x,elems, num.of.nths = 1,descending = FALSE,na.rm = FALSE,
    	index.return = FALSE, parallel = FALSE)
    rownth(x,elems, num.of.nths = 1,descending = FALSE,na.rm = FALSE,
    	index.return = FALSE, parallel = FALSE)
    nth(x, k, num.of.nths = 1,descending = FALSE,index.return = FALSE,na.rm = FALSE)

### Arguments

`x` | A matrix with the data.
`elems` | An integer vector with the kth smallest number to be returned for each column/row.
`k` | The kth smallest/biggest number to be returned.
`num.of.nths` | The number of the returned nths. By default is 1. Not use with argument parallel, for now.
`descending` | A boolean value (TRUE/FALSE) for descending order (biggest number). By default is ascending (smallest number).
`index.return` | Return the index of the kth smallest/biggest number.
`parallel` | Do you want to do it in parallel in C++? TRUE or FALSE only for col-row wise.
`na.rm` | TRUE or FAlSE for remove NAs if exists. Only for function "nth".

### Details

The functions is written in C++ in order to be as fast as possible.

### Value

For "colnth" , "rownth": A vector with the column/row nth

For "nth": The nth value.

### Author(s)

Manos Papadakis <papadakm95@gmail.com>

R implementation and documentation: Michail Tsagris <mtsagris@yahoo.gr> and Manos Papadakis <papadakm95@gmail.com>.

### See Also

`Median, colMedians, colMeans (buit-in R function)`

### Examples

    x <- matrix( rnorm(100 * 100), ncol = 100 )
    elems <- sample(1:100,100,TRUE)
    system.time( colnth(x,elems) )
    system.time( rownth(x,elems) )
    x <- rnorm(1000)
    nth(x, 500)
    sort(x)[500]

    x<-elems<-NULL

[Package Rfast version 2.0.0 Index]