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From |
László Sándor <sandorl@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
st: spmat: banded matrix from inverse distances |

Date |
Fri, 1 Jul 2011 13:59:08 -0400 |

Hi all, I am using Stata 11.2 on Unix and mac, and have another question relating to -sppack-. I got an answer from Rafal about keeping my spatial correlation matrix manageable if I only care about adjacency -- as then I can use a friendship list while importing to spmat, and that matrix can be banded from the outset, which is a must for me as I have no fewer than 401,639 observations. http://www.stata.com/statalist/archive/2011-06/msg00882.html However, as my data describes peers with overlapping spells (in prison cell, for that matter), I would try to keep track of their "inverse distance" too, which could be say, the number of their days overlapping. As this would be an integer, thus 2 bytes, even if I need to keep a band of 500, say, I would still keep the size of the banded matrix below 400 MB, I hope. Using an implementation of a useful sorting from graph theory, I think I could code up populating a matrix of the inverse distances outside of Stata. My question is, how would that data become useful for -spreg-? (The algorithm: https://networkx.lanl.gov/trac/ticket/530) Rafal wrote that -spmat use- can only work with files generated by -spmat- (after an import, say). Does it also imply that there is no functionality similar to -spmat import ..., nlist- with the bands with standard -spmat import-, with distances (row-by-row, within the bands)? The -spmat import- help file seems to imply otherwise first, though then only mentions the bands for its nlist option further down... "By default, spmat import imports data from a space-delimited text file in which the first line contains the number of columns of the spatial-weighting matrix and, if applicable, the lower and upper band, followed by the matrix stored row-by-row with unique place identifiers recorded in the first column." "nlist specifies that the text file is in the neighbor-list format. The first line of the file must contain the total number of places and, if the matrix is banded, the lower and upper band. Each remaining line lists a place ID followed by its neighbors, if any." Also, I'd be happy to import the inverse distance right away, as those can be kept integers, while the "distances" in this case would be needlessly bloated floats. Thank you very much again, Laszlo * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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