[R] diag() problem

[Duncan Murdoch]

On 10/19/2005 10:55 AM, Robin Hankin wrote:
> Hi
> 
> I have a matrix "u", for which diag() gives an error:
> 
> u <- structure(c(5.42334674128216, -2.31319389204264, -5.83059042218476,
>   -1.64112369640695, -2.31319389212801, 3.22737617646609,  
> 1.85200668021569,
>   -0.57102273078531, -5.83059042231881, 1.85200668008156,  
> 11.9488923894962,
>   -3.5525537165941, -1.64112369587405, -0.571022730886046,  
> -3.55255371755604,
>   10.0989829379577), .Dim = c(4, 4), .Dimnames = list(c("constant",
>   NA, NA, NA), c("constant", NA, NA, NA)))
> 
>  > u
>            constant       <NA>      <NA>       <NA>
> constant  5.423347 -2.3131939 -5.830590 -1.6411237
> <NA>     -2.313194  3.2273762  1.852007 -0.5710227
> <NA>     -5.830590  1.8520067 11.948892 -3.5525537
> <NA>     -1.641124 -0.5710227 -3.552554 10.0989829
>  > is.matrix(u)
> [1] TRUE
>  > diag(u)
> Error in if (is.list(nms) && !any(sapply(nms, is.null)) && all((nm <-  
> nms[[1]][1:m]) ==  :
>      missing value where TRUE/FALSE needed
> 
>  >
> 
> 
> What's going on here?

It's trying to check whether the row names match the column names, in 
which case it will assign those names to the diagonal elements.  But the 
writer didn't figure someone would have NA names, so the test

all((nm <- nms[[1]][1:m]) == nms[[2]][1:m])

fails.

It could be "fixed" by putting "na.rm=TRUE" into the all(), but that's 
probably not right:

 > all(c(1, NA) == c(1, 2), na.rm = TRUE)
[1] TRUE

I think we want to wrap the values in "paste", to convert to non-missing 
characters.  That would be

all(paste((nm <- nms[[1]][1:m])) == paste(nms[[2]][1:m]))

and would give

 > diag(u)
  constant      <NA>      <NA>      <NA>
  5.423347  3.227376 11.948892 10.098983

Any objections to me committing this change?

Duncan Murdoch