Code that only sometimes spits out a warning message in R

Question

I've got a very strange problem in R. I'm trying to run a plm with a certain panel data.frame. If i run the model, sometimes there's warning and sometimes there isn't. How is that possible? If i type class(mydf), exactly the same thing, only sometimes a warning. Does anyone know what this is about?

class(mydf)
[1] "data.frame"
Warning messages:
1: In if (is.na(le)) { :
  the condition has length > 1 and only the first element will be used
2: In if (is.na(le)) " __no length(.)__ " else if (give.length) { :
  the condition has length > 1 and only the first element will be used
3: In if (le > 0) paste0("[1:", paste(le), "]") else "(0)" :
  the condition has length > 1 and only the first element will be used
class(mydf)
[1] "data.frame"

Is this in the standard R GUI? RStudio? The terminal? All objects or just this particular data.frame? — MrFlick, May 08 '14 at 19:04
You need to make your problem reproducible, we are just as lost as you right now. — Paul Hiemstra, May 08 '14 at 19:11
There is an answer to this [here](http://stackoverflow.com/questions/21364221/plm-model-within-warning-messages-in-r) — Rich Scriven, May 08 '14 at 21:18

score 1 · Answer 1 · answered May 08 '14 at 21:57

1

I don't think the cited page explains why this is happening at all. There is a bug somewhere. The code should be tracked down and the offending lines fixed:

if (is.na(le)) " __no length(.)__ " else if (give.length) {

.... should be changed to:

if ( all(is.na(le)) ) " __no length(.)__ " else if (give.length) {

I agree with Paul that you should make this reproducible.

answered May 08 '14 at 21:57

IRTFM

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It's reproducible with `data("Produc", package = "plm")` – Rich Scriven May 08 '14 at 22:02
When the data prints, take a look at line 419 – Rich Scriven May 08 '14 at 22:08
Maybe it's a Windows-specific R bug or an old-R bug? When I execute: ` data("Produc", package = "plm"); class(Produc)` I get no warning. – IRTFM May 08 '14 at 22:11
The function was completely re-written last year. I think I may have found the problem though. Or at least an idea where it occurs – Rich Scriven May 08 '14 at 22:40
So the poster (or you?) is using an out-of-date version? – IRTFM May 09 '14 at 00:24
No, the things bad. I just installed `plm` today and I got the warnings. – Rich Scriven May 09 '14 at 00:29

score 0 · Answer 2 · answered Jun 02 '14 at 19:44

This is because str checks the length of its object and some objects, say the extended formulas from the Formula package does not have a single length. In particular, Formula:::length.Formula returns a vector rather than a number, which causes the warning. While you may not call str yourself, perhaps your IDE, say RStudio, may use it to show the object structure of objects in the workspace.

Code that only sometimes spits out a warning message in R

2 Answers2