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Re: NaN and missing values
From: |
heberf |
Subject: |
Re: NaN and missing values |
Date: |
Thu, 23 Sep 1999 13:29:02 -0500 (CDT) |
In SAS if you perform any mathematical operation on a missing value it returns
a
missing value and generates a warning (this is why it seems similar to NaN).
Of course SAS is not a matrix language so it really only deals with scalar
operations. Following this rule makes sense for all the element by element
operations (+,-,.*,./,exp,log,etc) but if you stuck to this rule for matrix
operations then matrix multiplation would put a missing value in the result
matrix whenever there is any missing value in the corrosponding row or column
of
the two matrices being multiplied. Matrix division (equation solving) makes no
sense at all. For stats functions you could drop rows as I said before and
then
do normal matrix operations.
Heber
> What functions make sense for missing data? Stats functions, I can
> understand, but I don't think it makes sense to add a matrix with
> missing data to a full matrix, for example. Adding to matrices with
> data missing in the same locations might make sense though. What do
> other systems (SAS, SPSS, S-plus, R, etc.) allow?
>
> jwe
>
>
>
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