persp is a generic function.
persp(x, ...)
"persp"(x = seq(0, 1, length.out = nrow(z)), y = seq(0, 1, length.out = 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", ...)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.NAs are
allowed). Note that x can be used instead of z for
convenience.title.theta gives the azimuthal direction and phi
the colatitude.d greater
than 1 will lessen the perspective effect and values less
and 1 will exaggerate it.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.z
coordinates. Often used with 0 < expand < 1 to shrink the
plotting box in the z direction.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
and lphi, the surface is shaded as though it was being
illuminated from the direction specified by azimuth ltheta
and colatitude lphi.((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.TRUE.TRUE. If box is FALSE then no
ticks or labels are drawn."simple" draws just an arrow
parallel to the axis to indicate direction of increase;
"detailed" draws normal ticks as per 2D plots.ticktype is "simple".par).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 homogeneous 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
function trans3d().
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.
The sizes and fonts of the axis labels and the annotations for
ticktype = "detailed" are controlled by graphics parameters
"cex.lab"/"font.lab" and
"cex.axis"/"font.axis" respectively.
The bounding box is drawn with edges of faces facing away from the viewer (and hence at the back of the box) with solid lines and other edges dashed and on top of the surface. This (and the plotting of the axes) assumes that the axis limits are chosen so that the surface is within the box, and the function will warn if this is not the case.
contour and image; trans3d.Rotatable 3D plots can be produced by package \href{https://CRAN.R-project.org/package=#1}{\pkg{#1}}rglrgl: other ways to produce static perspective plots are available in packages \href{https://CRAN.R-project.org/package=#1}{\pkg{#1}}latticelattice and \href{https://CRAN.R-project.org/package=#1}{\pkg{#1}}scatterplot3dscatterplot3d.
require(grDevices) # for trans3d
## 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, pmat = res), col = 2, pch = 16)
lines (trans3d(x, y = 10, z = 6 + sin(x), pmat = 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)
# (4) Surface colours corresponding to z-values
par(bg = "white")
x <- seq(-1.95, 1.95, length = 30)
y <- seq(-1.95, 1.95, length = 35)
z <- outer(x, y, function(a, b) a*b^2)
nrz <- nrow(z)
ncz <- ncol(z)
# Create a function interpolating colors in the range of specified colors
jet.colors <- colorRampPalette( c("blue", "green") )
# Generate the desired number of colors from this palette
nbcol <- 100
color <- jet.colors(nbcol)
# Compute the z-value at the facet centres
zfacet <- z[-1, -1] + z[-1, -ncz] + z[-nrz, -1] + z[-nrz, -ncz]
# Recode facet z-values into color indices
facetcol <- cut(zfacet, nbcol)
persp(x, y, z, col = color[facetcol], phi = 30, theta = -30)
par(op)
Run the code above in your browser using DataLab