Dear Meng,
Thanks for your message. It sounds like the sample size limitation
may be driven by memory allocation, which can be changed with
memory.limit(), or the amount of RAM on the computer itself. Note
that there can be some limitations to manipulating very large datasets
within R.
I'm not entirely sure about the second error message. If you have
missing data, I'd try subsetting the dataframe to fully-observed
units, as it may be driven by the way that match.data() handles
missing covariates.
Dan
On 2/7/06, Xu, Meng <XuM(a)ccf.org> wrote:
Dear Dr. Ho,
I am a biostatistician in the "Department of Quantitative Health Sciences"
of Cleveland Clinic Foundation. I am trying to use MatchIt to do the optimal
matching and encountering two questions:
Can you tell me the limit of the sample size for using MatchIt? My control
is 18000, and I always got the error message of "Error: cannot allocate
vector of size 7492 Kb"
When I cut the sample size, it worked and I could get m.out. But when I try
to use match.data(m.out) to retrieve the data, I got the error message of
"Error in data.frame(..., check.names = FALSE) : arguments imply differing
number of rows: 3302, 3125".
Thank you very much for helping me with this.
Meng
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