[R] Sanity check in loading large dataframe

[Luigi Marongiu]

Hello,
I am using a large spreadsheet (over 600 variables).
I tried `str` to check the dimensions of the spreadsheet and I got
```
> (str(df))
'data.frame': 302 obs. of  626 variables:
 $ record_id                 : int  1 1 1 1 1 1 1 1 1 1 ...
....
$ v1_medicamento___aceta    : int  1 NA NA NA NA NA NA NA NA NA ...
  [list output truncated]
NULL
```
I understand that `[list output truncated]` means that there are more
variables than those allowed by str to be displayed as rows. Thus I
increased the row's output with:
```

> (str(df, list.len=1000))
'data.frame': 302 obs. of  626 variables:
 $ record_id                 : int  1 1 1 1 1 1 1 1 1 1 ...
...
NULL
```

Does `NULL` mean that some of the variables are not closed? (perhaps a
missing comma somewhere)
Is there a way to check the sanity of the data and avoid that some
separator is not in the right place?
Thank you



-- 
Best regards,
Luigi