[R] replace NULL with NA in matrix

[Prof Brian Ripley]

On Thu, 17 Apr 2008, Uwe Ligges wrote:

> Tim Smith wrote:
>> Hi,
>>
>> I had a matrix with NULL values, which I wanted to replace with NA. Is there an efficient way to do this?
>>
>> Small sample input matrix:
>>         A       B       C       D       E
>> 1 5222.18 6355.10 4392.68 2607.41 4524.09
>> 2    NULL  257.33    NULL  161.51  119.44
>> 3    NULL  274.80  305.28  443.27    NULL
>> 4 1759.76 1556.45 1224.06 1558.73 1837.09
>
>
> How is it possible to construct such a matrix?

> A <- matrix(list(5222.18, NULL, NULL, 1759.76), 4, 1)
> A
      [,1]
[1,] 5222.18
[2,] NULL
[3,] NULL
[4,] 1759.76

A[sapply(A, is.null)] <- NA
A
      [,1]
[1,] 5222.18
[2,] NA
[3,] NA
[4,] 1759.76

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595