[R] Convert back to lower triangular matrix

[Bert Gunter]

1. Please post in plain text, not HTML (as the posting guide asks!)

2. This might actually be an R question -- is
?lower.tri
what you want?

-- Bert

On Tue, Nov 15, 2011 at 2:50 PM, Jeff Newmiller
<jdnewmil at dcn.davis.ca.us> wrote:
> This is R-help, not the linear algebra hotline. Please stay on topic.
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> Juliet Ndukum <jpntsang at yahoo.com> wrote:
>
>>Given a vector;> ab = seq(0.5,1, by=0.1)> ab[1] 0.5 0.6 0.7 0.8 0.9 1.0
>>The euclidean distance between the vector elements is given by the
>>lower triangular matrix�> dd1 = dist(ab,"euclidean")> dd1� � 1 � 2 � 3
>>� 4 � 52 0.1 � � � � � � � �3 0.2 0.1 � � � � � �4 0.3 0.2 0.1 � � � �5
>>0.4 0.3 0.2 0.1 � �6 0.5 0.4 0.3 0.2 0.1
>>Convert the lower triangular matrix to a full matrix> ddm =
>>as.matrix(dd1)> ddm� � 1 � 2 � 3 � 4 � 5 � 61 0.0 0.1 0.2 0.3 0.4 0.52
>>0.1 0.0 0.1 0.2 0.3 0.43 0.2 0.1 0.0 0.1 0.2 0.34 0.3 0.2 0.1 0.0 0.1
>>0.25 0.4 0.3 0.2 0.1 0.0 0.16 0.5 0.4 0.3 0.2 0.1 0.0
>>I would be grateful if someone could provide me with a code to convert
>>ddm to the lower triangular matrix as before i.e. dd1
>> above.
>>Your help will be greatly appreciated.JN
>>       [[alternative HTML version deleted]]
>>
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-- 

Bert Gunter
Genentech Nonclinical Biostatistics

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