On 11/08/11 13:27, David Winsemius wrote:
On Aug 10, 2011, at 9:22 PM, Rolf Turner wrote:
On 11/08/11 13:11, David Winsemius wrote:
On Aug 10, 2011, at 8:23 PM, Andra Isan wrote:
Hi All,
I would like to create a matrix in R but I dont know the size of my
matrix. I only know the size of the columns but not the size of the
rows. So, is there any way to create a dynamic matrix of size NULL
by n_cols? and then add to that matrix?
I know for a vector, I can do this: x= NULL but is there any way to
do the same for a matrix as well?
No. You cannot make an R matrix without knowing the number of rows.
By definition an R matix has two integer dimensions. Alternatives:
You can rbind to an existing matrix, or you can make a larger than
necessary matrix filled with NA's and then fill and later extract a
subset of the rows.
Wrong-oh, David. :-) Check this out:
0 is an integer.
Yes it is. But you are being pedantic. My suggestion does exactly
what I am sure the OP wanted.
He used the phrase ``NULL by n_cols'' simply because of unclear
thinking. What he wanted was an
``empty matrix'', with no rows and a given number of columns. Which is
what I gave him.
It is interesting that the syntax works with matrices but not with data
frames. If you want an
empty data frame, with no rows and a given number of columns, you need
to create a matrix,
in the manner indicated, and then use as.data.frame, which yields the
desired result.
cheers,
Rolf
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