[R] Checking if a matrix exists/is defined

[Johannes Huesing]

Steven Yen <syen04 at gmail.com> [Sun, Oct 19, 2014 at 06:17:48AM CEST]:
> Hello
> Can someone help me with the following, specifically in judging 
> whether a matrix exists. 

exists(my.matrix)

> I have trouble with the first line below. In 
> this case, matrix obj$hessian exists and is 74 x 74. I receive the 
> error message:
> 
> Warning message:

Looks like a warning message to me.

> In all(w$hessian) : coercing argument of type 'double' to logical
> 

all expects a logical vector, instead it finds a double vector. Trying
to make sense of it, it converts the double vector to logical using
as.logical(). Looking up ?as.logical I fail, however, to see which
rules it uses to convert double to logical. Possibly 0 -> FALSE and
everything else -> TRUE.

-- 
Johannes Hüsing               There is something fascinating about science. 
                              One gets such wholesale returns of conjecture 
mailto:johannes at huesing.name  from such a trifling investment of fact.                
http://derwisch.wikidot.com         (Mark Twain, "Life on the Mississippi")