Notice that 6,000 down there. Should be 60,000. Also, I'm pretty sure that
this works based on the population of the old object, not the new one.
Proportion Avg
Computes the average based on the proportion of values from the covered
areas (weighs the averages according to area). For example, if 80% of a
new object's area is from Object A having a mortality rate of .8% and 20%
of the new object's area is from Object B having a birth mortality rate of
.65%, then the birth rate of the object would be equal to .8 x .008 +
.0065 x .2 = .0077 or .77%
Proportion WtAvg
Computes the average based on the proportion of values from the covered
areas (weighs the averages according to another field whose value is
proportioned). For example, (continuing from the example above),
Population of the new object, Object A = 34,000. Population of new
object, Object B = 26,000. The birth mortality rate is (.8 x 34,000 + .6
x 26,000) /6,000 = .713.
On Thu, 3 Feb 2000, Marjorie Roswell wrote:
> We did analysis by census tracts: Our statistician predicted number of
> cases of lead poisoning per 1000. Now they want the results by zip code.
>
> Yup: years ago, when I was a heavy MapInfo programmer, I did this sort of
> thing all the time. Now I'm afraid I might forget. Considering the request
> came today, and the turnaround time is tomorrow, I'm asking for assistance
> today in updating my zip code file by the sum of all the proportional
> parts of the census tract.
>
> I've used the update columns command, and now my mapbasic window reads:
>
> Add Column "Zplowres" (propoverlap )From Mdtr Set To proportion
> sum(Pop_90) Where within
>
> Is this the right code?
>
> I'm getting the usual "error overlaying objects." and I get bunches of zip
> codes that show up with a population of 0.
>
> I've got Mapinfo 5.0. Vague recollection that despite other problems the
> error overlay problem is resolved in more recent versions?
>
> Can I FIX the problem with some utility, or can I only FIND the
> problematic areas?
>
> BTW, the Baltimore Sun did a bunch of editorials on lead problems, and
> it's suddenly of great interest to the governor's office, hence the quick
> turn-around time... (and the fact that I'm in class next week.)
>
> In summary:
>
> What's the right code?
> What do I do about the error overlaying objects problem?
>
> (Yes: I'll search the archives for answers, too..)
>
> Your 9-projects-at-once-busy colleague,
>
> Margie
>
>
>
>
>
>
> _________________________________________________________
> Marjorie Roswell, Spatial Analyst
> UMBC Center for Health Program Development and Management
> 1000 Hilltop Circle Fx: (410)455-6850
> Baltimore, MD 21250 E: [EMAIL PROTECTED]
> Ph: (410)455-6802 http://umbc.edu/~roswell/mipage.html
> _________________________________________________________
>
> ----------------------------------------------------------------------
> To unsubscribe from this list, send e-mail to [EMAIL PROTECTED] and put
> "unsubscribe MAPINFO-L" in the message body, or contact [EMAIL PROTECTED]
>
_________________________________________________________
Marjorie Roswell, Spatial Analyst
UMBC Center for Health Program Development and Management
1000 Hilltop Circle Fx: (410)455-6850
Baltimore, MD 21250 E: [EMAIL PROTECTED]
Ph: (410)455-6802 http://umbc.edu/~roswell/mipage.html
_________________________________________________________
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To unsubscribe from this list, send e-mail to [EMAIL PROTECTED] and put
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