# knn3

From caret v5.15-045
by Max Kuhn

##### k-Nearest Neighbour Classification

$k$-nearest neighbour classification that can return class votes for all classes.

- Keywords
- multivariate

##### Usage

```
## S3 method for class 'formula':
knn3(formula, data, subset, na.action, k = 5, ...)
```## S3 method for class 'matrix':
knn3(x, y, k = 5, ...)

## S3 method for class 'data.frame':
knn3(x, y, k = 5, ...)

knn3Train(train, test, cl, k=1, l=0, prob = TRUE, use.all=TRUE)

##### Arguments

- formula
- a formula of the form
`lhs ~ rhs`

where`lhs`

is the response variable and`rhs`

a set of predictors. - data
- optional data frame containing the variables in the model formula.
- subset
- optional vector specifying a subset of observations to be used.
- na.action
- function which indicates what should happen when
the data contain
`NA`

s. - k
- number of neighbours considered.
- x
- a matrix of training set predictors
- y
- a factor vector of training set classes
- ...
- additional parameters to pass to
`knn3Train`

. However, passing`prob = FALSE`

will be over--ridden. - train
- matrix or data frame of training set cases.
- test
- matrix or data frame of test set cases. A vector will be interpreted as a row vector for a single case.
- cl
- factor of true classifications of training set
- l
- minimum vote for definite decision, otherwise
`doubt`

. (More precisely, less than`k-l`

dissenting votes are allowed, even if`k`

is increased by ties.) - prob
- If this is true, the proportion of the votes for each class
are returned as attribute
`prob`

. - use.all
- controls handling of ties. If true, all distances equal to the
`k`

th largest are included. If false, a random selection of distances equal to the`k`

th is chosen to use exactly`k`

neighbours.

##### Details

`knn3`

is essentially the same code as `ipredknn`

and `knn3Train`

is a copy of `knn`

. The underlying
C code from the `class`

pacakge has been modifed to return the vote
percentages for each class (previously the percentage for the winning
class was returned).

##### Value

- An object of class
`knn3`

. See`predict.knn3`

.

##### Examples

```
irisFit1 <- knn3(Species ~ ., iris)
irisFit2 <- knn3(as.matrix(iris[, -5]), iris[,5])
data(iris3)
train <- rbind(iris3[1:25,,1], iris3[1:25,,2], iris3[1:25,,3])
test <- rbind(iris3[26:50,,1], iris3[26:50,,2], iris3[26:50,,3])
cl <- factor(c(rep("s",25), rep("c",25), rep("v",25)))
knn3Train(train, test, cl, k = 5, prob = TRUE)
```

*Documentation reproduced from package caret, version 5.15-045, License: GPL-2*

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