persp {graphics} | R Documentation |

This function draws perspective plots of surfaces over the
x–y plane. `persp`

is a generic function.

persp(x, ...) ## Default S3 method: persp(x = seq(0, 1, len = nrow(z)), y = seq(0, 1, len = ncol(z)), z, xlim = range(x), ylim = range(y), zlim = range(z, na.rm = TRUE), xlab = NULL, ylab = NULL, zlab = NULL, main = NULL, sub = NULL, theta = 0, phi = 15, r = sqrt(3), d = 1, scale = TRUE, expand = 1, col = "white", border = NULL, ltheta = -135, lphi = 0, shade = NA, box = TRUE, axes = TRUE, nticks = 5, ticktype = "simple", ...)

`x, y` |
locations of grid lines at which the values in `z` are
measured. These must be in ascending order. By default, equally
spaced values from 0 to 1 are used. If `x` is a `list` ,
its components `x$x` and `x$y` are used for `x`
and `y` , respectively. |

`z` |
a matrix containing the values to be plotted (`NA` s are
allowed). Note that `x` can be used instead of `z` for
convenience. |

`xlim, ylim, zlim` |
x-, y- and z-limits. The plot is produced so that the rectangular volume defined by these limits is visible. |

`xlab, ylab, zlab` |
titles for the axes. N.B. These must be character strings; expressions are not accepted. Numbers will be coerced to character strings. |

`main, sub` |
main and sub title, as for `title` . |

`theta, phi` |
angles defining the viewing direction.
`theta` gives the azimuthal direction and `phi`
the colatitude. |

`r` |
the distance of the eyepoint from the centre of the plotting box. |

`d` |
a value which can be used to vary the strength of
the perspective transformation. Values of `d` greater
than 1 will lessen the perspective effect and values less
and 1 will exaggerate it. |

`scale` |
before viewing the x, y and z coordinates of the
points defining the surface are transformed to the interval
[0,1]. If `scale` is `TRUE` the x, y and z coordinates
are transformed separately. If `scale` is `FALSE`
the coordinates are scaled so that aspect ratios are retained.
This is useful for rendering things like DEM information. |

`expand` |
a expansion factor applied to the `z`
coordinates. Often used with `0 < expand < 1` to shrink the
plotting box in the `z` direction. |

`col` |
the color(s) of the surface facets. Transparent colours are
ignored. This is recycled to the (nx-1)(ny-1) facets. |

`border` |
the color of the line drawn around the surface facets.
The default, `NULL` , corresponds to `par("fg")` .
A value of `NA` will disable the drawing of borders: this is
sometimes useful when the surface is shaded. |

`ltheta, lphi` |
if finite values are specified for `ltheta`
and `lphi` , the surface is shaded as though it was being
illuminated from the direction specified by azimuth `ltheta`
and colatitude `lphi` . |

`shade` |
the shade at a surface facet is computed as
`((1+d)/2)^shade` , where `d` is the dot product of
a unit vector normal to the facet and a unit vector in the
direction of a light source. Values of `shade` close
to one yield shading similar to a point light source model
and values close to zero produce no shading. Values in the
range 0.5 to 0.75 provide an approximation to daylight
illumination. |

`box` |
should the bounding box for the surface be displayed.
The default is `TRUE` . |

`axes` |
should ticks and labels be added to the box. The
default is `TRUE` . If `box` is `FALSE` then no
ticks or labels are drawn. |

`ticktype` |
character: `"simple"` draws just an arrow
parallel to the axis to indicate direction of increase;
`"detailed"` draws normal ticks as per 2D plots. |

`nticks` |
the (approximate) number of tick marks to draw on the
axes. Has no effect if `ticktype` is `"simple"` . |

`...` |
additional graphical parameters (see `par` ). |

The plots are produced by first transforming the
coordinates to the interval [0,1]. The surface is then viewed
by looking at the origin from a direction defined by `theta`

and `phi`

. If `theta`

and `phi`

are both zero
the viewing direction is directly down the negative y axis.
Changing `theta`

will vary the azimuth and changing `phi`

the colatitude.

There is a hook called `"persp"`

(see `setHook`

)
called after the plot is completed, which is used in the
testing code to annotate the plot page. The hook function(s) are
called with no argument.

Notice that `persp`

interprets the `z`

matrix as a table of
`f(x[i], y[j])`

values, so that the x axis corresponds to row
number and the y axis to column number, with column 1 at the bottom,
so that with the standard rotation angles, the top left corner of the
matrix is displayed at the left hand side, closest to the user.

`persp()`

returns the *viewing transformation matrix*, say
`VT`

, a *4 x 4* matrix suitable for projecting 3D coordinates
*(x,y,z)* into the 2D plane using homogenous 4D coordinates
*(x,y,z,t)*.
It can be used to superimpose additional graphical elements on the 3D
plot, by `lines()`

or `points()`

,
using the simple function `trans3d()`

.

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)
*The New S Language*.
Wadsworth & Brooks/Cole.

## More examples in demo(persp) !! ## ----------- # (1) The Obligatory Mathematical surface. # Rotated sinc function. x <- seq(-10, 10, length= 30) y <- x f <- function(x,y) { r <- sqrt(x^2+y^2); 10 * sin(r)/r } z <- outer(x, y, f) z[is.na(z)] <- 1 op <- par(bg = "white") persp(x, y, z, theta = 30, phi = 30, expand = 0.5, col = "lightblue") persp(x, y, z, theta = 30, phi = 30, expand = 0.5, col = "lightblue", ltheta = 120, shade = 0.75, ticktype = "detailed", xlab = "X", ylab = "Y", zlab = "Sinc( r )" ) -> res round(res, 3) # (2) Add to existing persp plot - using trans3d() : xE <- c(-10,10); xy <- expand.grid(xE, xE) points(trans3d(xy[,1], xy[,2], 6, pm = res), col = 2, pch =16) lines (trans3d(x, y=10, z= 6 + sin(x), pm = res), col = 3) phi <- seq(0, 2*pi, len = 201) r1 <- 7.725 # radius of 2nd maximum xr <- r1 * cos(phi) yr <- r1 * sin(phi) lines(trans3d(xr,yr, f(xr,yr), res), col = "pink", lwd=2)## (no hidden lines) # (3) Visualizing a simple DEM model z <- 2 * volcano # Exaggerate the relief x <- 10 * (1:nrow(z)) # 10 meter spacing (S to N) y <- 10 * (1:ncol(z)) # 10 meter spacing (E to W) ## Don't draw the grid lines : border = NA par(bg = "slategray") persp(x, y, z, theta = 135, phi = 30, col = "green3", scale = FALSE, ltheta = -120, shade = 0.75, border = NA, box = FALSE) par(op)

[Package *graphics* version 2.2.1 Index]