Why is R saying "argument is of length zero" and how can I fix this?-CodePudding

R will plot the Venn diagrams and shaded areas correctly, but it will not say A or A' in the console. The image below is an example of what I'm trying to have done. Note that the function "venn" is used from the "venn" package: https://cran.r-project.org/web/packages/venn/venn.pdf

Example of preferred output in the console

genvd = function(x){
  x = venn(x,zcolor = "blue",ilabels = F)
  
  if (x == "A") {
    print("A",quote = FALSE)
    return(x)
  }
  else if (x == "~A") {
    print("A'",quote = FALSE)
    return(x)
  }
}

genvd("A")
genvd("~A")

Error Code:

Error in if (x == "A") { : argument is of length zero

CodePudding user response：

The error comes from the usage of condition on the venn object instead of the original input. We could assign it to a new object. In addition, print doesn't have any return value.

genvd <- function(x){
  
  venn::venn(x,zcolor = "blue",ilabels = FALSE)
  
  if (x == "A") {
    print("A",quote = FALSE)
    
  }
  else if (x == "~A") {
     print("A'",quote = FALSE)
    
  }
}

The venn object is not returning anything

> tmp <- venn("A", zcolor = "blue", ilabels = FALSE)
> str(tmp)
 NULL

-testing

> genvd("A")
[1] A
> genvd("~A")
[1] A'