I have some matrices stored as elements in a list that I am working
with. On example is provided below as TP[[18]] 

> TP[[18]]
      level2
level1  1  2  3  4
     1 79  0  0  0
     2  0  0  0  0
     3  0  0  0  0
     4  0  0  0  0

Now, using prop.table on this gives

> prop.table(TP[[18]],1)
      level2
level1   1   2   3   4
     1   1   0   0   0
     2                
     3                
     4      

It is important for the zero's to retain their position as this matrix
will subsequently be used in some matrix multiplication and hence, must
be of dimension 4 by 4 so that is it conformable for multiplcation with
another matrix.
 
In looking at the structure of the object resulting from prop.table I
see NaNs, and so I can do this

> rr <- TP[[18]]
> rr[is.na(rr)] <- 0
> rr
      level2
level1  1  2  3  4
     1 79  0  0  0
     2  0  0  0  0
     3  0  0  0  0
     4  0  0  0  0

This is exactly what I want for each matrix. But, I have multiple
matrices stored within the list that need to be changed and so I am
trying to resolve this via lapply, but something is awry (namely the
user), but I could use a little help.

I was thinking the following function should work, but it doesn't. It
reduces each matrix within the list to a 0.

PP <- lapply(TP, function(x) x[is.na(x)] <- 0)

Am I missing something obvious?

Harold


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