# plotEqn3d

##### Plot Linear Equations in 3D

Shows what matrices \(A, b\) look like as the system of linear equations, \(A x = b\) with three unknowns, x1, x2, and x3, by plotting a plane for each equation.

##### Usage

```
plotEqn3d(A, b, vars, xlim = c(-2, 2), ylim = c(-2, 2), zlim,
col = 2:(nrow(A) + 1), alpha = 1, labels = FALSE,
solution = TRUE, axes = TRUE, lit = FALSE)
```

##### Arguments

- A
either the matrix of coefficients of a system of linear equations, or the matrix

`cbind(A,b)`

The`A`

matrix must have three columns.- b
if supplied, the vector of constants on the right hand side of the equations, of length matching the number of rows of

`A`

.- vars
a numeric or character vector of names of the variables. If supplied, the length must be equal to the number of unknowns in the equations. The default is

`paste0("x", 1:ncol(A)`

.- xlim
axis limits for the first variable

- ylim
axis limits for the second variable

- zlim
horizontal axis limits for the second variable; if missing,

`zlim`

is calculated from the range of the set of equations over the`xlim`

and`ylim`

- col
scalar or vector of colors for the lines, recycled as necessary

- alpha
transparency applied to each plane

- labels
logical, or a vector of character labels for the equations; not yet implemented.

- solution
logical; should the solution point for all equations be marked (if possible)

- axes
logical; whether to frame the plot with coordinate axes

- lit
logical, specifying if lighting calculation should take place on geometry; see

`rgl.material`

##### Value

nothing; used for the side effect of making a plot

##### References

Fox, J. and Friendly, M. (2016). "Visualizing Simultaneous Linear Equations, Geometric Vectors, and
Least-Squares Regression with the matlib Package for R". *useR Conference*, Stanford, CA, June 27 - June 30, 2016.

##### Examples

```
# NOT RUN {
# three consistent equations in three unknowns
A <- matrix(c(13, -4, 2, -4, 11, -2, 2, -2, 8), 3,3)
b <- c(1,2,4)
plotEqn3d(A,b)
# }
```

*Documentation reproduced from package matlib, version 0.9.2, License: GPL (>= 2)*