Question

I have a strange issue with subset: it doesn’t recognize the variables in my dataframe.

For example, if I want a summary of the variable v1 in the dataframe DF, I get:

summary(DF$v1)

 Min.    1st Qu. Median  Mean   3rd Qu. Max
-123.00  4.00    14.00   84.62  49.00   13140.00 

Now, this variable should always be non-negative, so I want to inspect the negative values by subsetting the dataframe DF into the dataframe PROBS. But if I try this:

PROB <- subset[DF, v1 < 0]

I get:

Error: object "v1" not found

I am positive that I am not misspelling this variable name. I have tried with other variables in this dataframe, but it keeps throwing this error at me.

Does anyone have any idea about the reason for such a strange behaviour? I have never had any problem with the subset function!

Thanks.

Answer 1

Subset is a function, so you should use subset(DF, v1 < 0) instead of the square brackets.

Square brackets are used for subsetting dataframes or matrices directly. subset[DF, v1 < 0] is trying to subset the subset function by looking for the variable v1 within the scope of the subset object. The object subset is a function, so it can’t find the v1 object.