Yes, here's one I made earlier:
In step 2 of Create Thematic Map choose the field selection "Expression" at
the bottom of the list.
Use the expression: population / area
In a large rural areas with low pop densities, you may have to use a
modified expression to get 'comfortable' figures for end-users to grasp:
give it in terms of population per 10 or 100 sq mi rather than 0.03 per sq
mi. But this always depends on your target audience: you're likely to know
what they can handle.
the resulting code from the create thematic map is:
shade window 9606588 1
with population * 1000 / area
ranges apply all use color
Brush (2,16711680,16777215)
1300: 4000 Brush (2,12632256,16777215) ,
4000: 6700 Brush (2,13668496,16777215) ,
6700: 9400 Brush (2,14704736,16777215) ,
9400: 12100 Brush (2,15740976,16777215) ,
12100: 14700 Brush (2,16711680,16777215)
default Brush (2,16711680,16777215)
# use 2 round 100000 inflect off Brush (2,16777215,16777215) at 2 by 0
color 1 #
set legend window 9606588
layer prev display on shades on symbols off lines off count on
title "J_gr by population/area" Font ("MS Sans Serif",0,10,0)
subtitle "" Font ("MS Sans Serif",0,8,0)
ascending off ranges Font ("MS Sans Serif",0,8,0)
"all others" display off ,
"1,300 to 4,000" display on ,
"4,000 to 6,700" display on ,
"6,700 to 9,400" display on ,
"9,400 to 12,100" display on ,
"12,100 to 14,700" display on
Incidentally, another way of showing population density - particularly in an
urban area like the one I work in - is to use a dot-density map on
population field (not the expression for population density). It's very
intuitive for the unsophisticated end-user.
Graham O'Brien (no known relation)
London UK
----- Original Message -----
From: Brendan O'Brien <[EMAIL PROTECTED]>
To: 'Mapinfo-L' <[EMAIL PROTECTED]>
Sent: Wednesday, March 08, 2000 5:20 PM
Subject: MI Thematic Mapping
>
>
>
> Hi all,
>
> I am talking the lazy way out of solving a problem.
>
> I have map layer of local geographical boundaries (DED's) which
> contain population, area, and id columns.
>
> I want to create a thematic map showing population density per sq mile
> over a range of values for each DED.
>
> Do I need to create an expression if so what?
>
> Regards,
>
> Brendan O'Brien
>
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