The error “error in dev.off() : cannot shut down device 1 (the null device)” occurs when the R programming language encounters an issue while trying to close a graphics device (device 1, which refers to the null device). The null device is a virtual graphics device that discards any displayed output.
To understand this error better, let’s consider an example:
plot(1:10) # generate a simple plot
dev.off() # try to close the current graphics device (device 1)
In the example above, a plot is created using the plot() function. Then, dev.off() is called to close the graphics device. However, if the null device (device 1) is already closed or encountered an issue, the “cannot shut down device 1 (the null device)” error is thrown.
It’s important to note that dev.off() is typically used to close the current graphics device when multiple devices are open. It is not necessary to explicitly call dev.off() for most plots or graphics operations.