R语言图像保存

Control Multiple Devices

Description

These functions provide control over multiple graphics devices.

Usage

dev.cur()
dev.list()
dev.next(which = dev.cur())
dev.prev(which = dev.cur())
dev.off(which = dev.cur())
dev.set(which = dev.next())
dev.new(...)
graphics.off()
Arguments

which 
An integer specifying a device number.

... 
arguments to be passed to the device selected.

Details

Only one device is the ‘active’ device: this is the device in which all graphics operations occur. There is a "null device" which is always open but is really a placeholder: any attempt to use it will open a new device specified by getOption("device")).

Devices are associated with a name (e.g., "X11" or "postscript") and a number in the range 1 to 63; the "null device" is always device 1. Once a device has been opened the null device is not considered as a possible active device. There is a list of open devices, and this is considered as a circular list not including the null device. dev.next and dev.prev select the next open device in the appropriate direction, unless no device is open.

dev.off shuts down the specified (by default the current) device. If the current device is shut down and any other devices are open, the next open device is made current. It is an error to attempt to shut down device 1. graphics.off() shuts down all open graphics devices. Normal termination of a session runs the internal equivalent of graphics.off().

dev.set makes the specified device the active device. If there is no device with that number, it is equivalent to dev.next. If which = 1 it opens a new device and selects that.

dev.new opens a new device. Normally R will open a new device automatically when needed, but this enables you to open further devices in a platform-independent way. (For which device is used see getOption("device").) Note that care is needed with file-based devices such as pdf and postscript and in that case file names such as ‘Rplots.pdf’, ‘Rplots1.pdf’, ..., ‘Rplots999.pdf’ are tried in turn. Only named arguments are passed to the device, and then only if they match the argument list of the device. Even so, care is needed with the interpretation of e.g. width, and for the standard bitmap devices units = "in", res = 72 is forced if neither is supplied but both width and height are.

Value

dev.cur returns a length-one named integer vector giving the number and name of the active device, or 1, the null device, if none is active.

dev.list returns the numbers of all open devices, except device 1, the null device. This is a numeric vector with a names attribute giving the device names, or NULL is there is no open device.

dev.next and dev.prev return the number and name of the next / previous device in the list of devices. This will be the null device if and only if there are no open devices.

dev.off returns the number and name of the new active device (after the specified device has been shut down).

dev.set returns the number and name of the new active device.

dev.new returns the return value of the device opened, usually invisible NULL.

See Also

Devices, such as postscript, etc.

layout and its links for setting up plotting regions on the current device.

Examples

## Not run: ## Unix-specific example
x11()
plot(1:10)
x11()
plot(rnorm(10))
dev.set(dev.prev())
abline(0, 1) # through the 1:10 points
dev.set(dev.next())
abline(h = 0, col = "gray") # for the residual plot
dev.set(dev.prev())
dev.off(); dev.off() #- close the two X devices

## End(Not run)