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I have a programme where I would like to do something slightly different if a certain df has already been created but the below won't work. Any suggestions? Also, would it be different for a matrix?

if (exists(df)) {
# do somthing    
} else {
# do other thing     
}
Joel B
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3 Answers3

3

Try this (you would need to put the variable name in "" (it needs to be a character string) for exists, e.g. "df"):

df <- data.frame(a = 3)

if (exists("df")) {
  print("df exists")
} else {
  print("df does not exist")
}

See documentation for exists.

Helix123
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0

You can use is.data.frame to check if there is already a dataframe 

if (is.data.frame(df)) {
# do somthing    
} else {
# do other thing     
}

You can use is.matrix with similar use.

Ronak Shah
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if (is.data.frame(df)) { 
# do stuff to df
} else {
# do other thing     
} 

if (is.matrix(mx)) { 
# do stuff to mx
} else {
# do other thing     
}
Joel B
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  • You should add some explication to your code to make a complete answer. Even correct, code only answers are not very legible. Here is how to write a good answer: https://stackoverflow.com/help/how-to-answer – Elzo Valugi Aug 16 '16 at 09:42