I think your NAControl function lacks of a target.

谢谢~
我试一下~

good luck!

bar2<-as.data.frame(bar) 然后x<-setNA(bar2,nc)

setNA(x, control, ...)

## S4 method for signature 'data.frame,NAControl'
setNA(x, control, i)
Arguments

x       
the data in which missing values should be inserted.
control       
a control object inheriting from the virtual class "VirtualNAControl" or a character string specifying such a control class (the default being "NAControl").
i       
an integer giving the element or row of the slot NArate of control to be used as missing value rate(s).
...       
if control is a character string or missing, the slots of the control object may be supplied as additional arguments. See "NAControl" for details on the slots.

Methods

x = "data.frame", control = "character"
set missing values using a control class specified by the character string control. The slots of the control object may be supplied as additional arguments.

x = "data.frame", control = "missing"
set missing values using a control object of class "NAControl". Its slots may be supplied as additional arguments.

x = "data.frame", control = "NAControl"
set missing values as defined by the control object control.