# ab.dist: Distance Functions for nearest neighbours In MuViCP: MultiClass Visualizable Classification using Combination of Projections

## Description

These functions compute Absolute (`ab.dist`), Euclidean (`eu.dist`) or Mahalanobis (`mh.dist`) distances between two points. The variant functions (`*.matY`), accomplish the same task, but between a point on the one hand, and every point specified as rows of a matrix on the other.

## Usage

 ```1 2 3 4 5 6``` ```ab.dist(x, y) eu.dist(x, y) mh.dist(x, y, A) ab.dist.matY(x, Y) eu.dist.matY(x, Y) mh.dist.matY(x, Y, A) ```

## Arguments

 `x` The vector (point) from which distance is sought. `y` The vector (point) to which distance is sought. `Y` A set of points, specified as rows of a matrix, to which distances are sought. `A` The inverse matrix to use for the Mahalanobis distance.

## Details

These functions are used internally to decide how the nearest neighbours shall be calculated; the user need not call any of these functions directly. Rather, the choice of distance is specified as a string ('euclidean' or 'absolute' or 'mahal').

## Value

Either a single number for the distance, or a vector of distances, corresponding to each row of `Y`.

Mohit Dayal

get.NN

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11``` ```x <- c(1,2) y <- c(0,3) mu <- c(1,3) Sigma <- rbind(c(1,0.2),c(0.2,1)) Y <- MASS::mvrnorm(20, mu = mu, Sigma = Sigma) ab.dist(x,y) eu.dist(x,y) mh.dist(x,y,Sigma) ab.dist.matY(x,Y) eu.dist.matY(x,Y) mh.dist.matY(x,Y,Sigma) ```

### Example output

```Warning message:
no DISPLAY variable so Tk is not available
 2
 2
[,1]
[1,]  2.5
 2.2284123 2.2378047 1.1964977 0.9432708 1.8059748 2.3870570 1.6303574
 2.5202570 0.7032441 2.7113114 1.7023114 2.7414863 2.1732236 1.5718124
 2.3493425 3.6400791 3.2157438 1.9691935 1.5027929 1.9431484
  2.7771813  3.4846290  0.9536751  0.4452661  1.9816146  3.2541393
  1.4036025  3.2927857  0.2529855  3.9744493  1.4643519  4.1670429
  2.3624025  1.8209725  2.8782691 11.6991019  5.3710730  1.9578152
  1.4690891  2.6461325
  3.3488639  3.9471429  0.8938424  0.3712160  1.7975297  2.8805821
  1.7234324  4.0672579  0.2132002  3.4365597  1.2267182  5.0383164
  2.9526064  2.0321842  3.5484347 11.8634240  4.5594646  2.4393717
  1.6947381  2.5210353
```

MuViCP documentation built on May 1, 2019, 7:56 p.m.