R help - May 2011 - How to store a triangular matrix

Hello, I want to create a triangular matrix and only keep the lower triangle
entries without having to allocate memory for the whole matrix, is there any way
I can do something like 
A<-matrix(data, nrow=50)
 but for a triangular matrix?


Thanks
ERV






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On May 13, 2011, at 10:52 AM, Estefania Ruiz Vargas wrote:
> Hello, I want to create a triangular matrix and only keep the lower  
> triangle entries without having to allocate memory for the whole  
> matrix, is there any way I can do something like
> A<-matrix(data, nrow=50)
>  but for a triangular matrix?
The `Matrix` package implements sparse matrices and has several  
triangular classes.

-- 

David Winsemius, MD
West Hartford, CT

Estefania, if you do something like

	your.matrix <- matrix(1, 50, 50)
	your.matrix[upper.tri(your.matrix)] <- NA

You will have NAs for the entire upper triangle. If you opt to do  

	your.matrix[upper.tri(your.matrix)] <- ""

The upper triangle will be empty but it will coerce data to be
'character' instead of 'numeric'. Hope it helps.


-----Mensagem original-----
De: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] Em
nome de Estefania Ruiz Vargas
Enviada em: sexta-feira, 13 de maio de 2011 11:53
Para: r-help at r-project.org
Assunto: [R] How to store a triangular matrix

Hello, I want to create a triangular matrix and only keep the lower triangle
entries without having to allocate memory for the whole matrix, is there any way
I can do something like A<-matrix(data, nrow=50)
?but for a triangular matrix?


Thanks
ERV






	[[alternative HTML version deleted]]


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