##### Determines if a point is on or left of the vector described by two other points.

A simple test function to determine the position of one (or more) points relative to a vector spanned by two points.

- Keywords
- utilities

##### Usage

```
on(x1, y1, x2, y2, x0, y0, eps = 1e-16)
left(x1, y1, x2, y2, x0, y0, eps = 1e-16)
```

##### Arguments

- x1
`x`

coordinate of first point determinig the vector.- y1
`y`

coordinate of first point determinig the vector.- x2
`x`

coordinate of second point determinig the vector.- y2
`y`

coordinate of second point determinig the vector.- x0
vector of

`x`

coordinates to locate relative to the vector \((x_2-x_1, y_2-y_1)\).- y0
vector of

`x`

coordinates to locate relative to the vector \((x_2-x_1, y_2-y_1)\).- eps
tolerance for checking if \(x_0,y_0\) is on or left of \((x_2-x_1, y_2-y_1)\), defaults to \(10^{-16}\).

##### Value

logical vector with the results of the test.

##### See Also

##### Examples

```
# NOT RUN {
y <- x <- c(0,1)
## should be TRUE
on(x[1],y[1],x[2],y[2],0.5,0.5)
## note the default setting of eps leading to
on(x[1],y[1],x[2],y[2],0.5,0.50000000000000001)
## also be TRUE
## should be TRUE
left(x[1],y[1],x[2],y[2],0.5,0.6)
## note the default setting of eps leading to
left(x[1],y[1],x[2],y[2],0.5,0.50000000000000001)
## already resulting to FALSE
# }
```

*Documentation reproduced from package interp, version 1.0-33, License: GPL (>= 2)*

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