As part of my continuous effort to understand what is selling where, I've begun analyzing 2007 residential sales per zip code per square. In other words, I've taken 2007 home and condo sales through August 2007 [the last full month of data I have in my database] and, for each zip code, determined sales for each square in the zip code.
For my first such analysis, I thought I'd look at zip code 20005, home to Logan Circle and part of historic Shaw. The area has undergone a lot of renovation and development in the past 10 years; I've reported on quite a few condos that have been built there since 2003 [Lofts 14, Lofts 14 Two, Saxon Court, etc.]. A good friend lives off of Logan Circle so I've spent a fair amount of time in the area in the past four years, which is striking because when I first lived in DC in the late 80s and early 90s, no one ventured to Logan Circle because it was considered a risky neighborhood.
Squares
All properties in the District - for that matter, everywhere in the US - are identified by the square and lot on which they are located. The map below shows the squares for zip code 20005 for which the District recorded sales through August 2007. For example, condos located on the 1400 block of Church St NW are on square 0209. For those who know the area, Whole Foods is on square 0210.

Sales
The district recorded 186 sales in zip code 20005. To be consistent with my previous analyses, I've excluded anything the District has not designated a home [rowhouse, detached, or semi-detached] or a condo, leaving 179 sales recorded through August 2007 [multifamily conversions are excluded because I cannot be certain they're truly single family homes]. It turns out that all 2007 sales for zip code 20005 have been condos; not one single family home has been sold in the zip code.
The chart below shows the distribution of sales in the area. As in previous analyses, more than half of the units sold [97 of 179, or 54.2%] were sold for $450,000 or less; $450,000 seems to be the magic number for the District.

According to the table below, square 0211 has the honor of having the highest average and median sales price recorded in the neighborhood, averaging $554/sq ft.

Total dollar volume for 2007 sales in 20005 is $82,103,001.
Heat Map

One thing I've always wanted to do is depict District sales using a heat map, i.e., using color to indicate price ranges on a spatial basis. My data is granular enough to allow me to 'heat map' the District on a per square basis. My challenge has been finding the right technology to do this at an affordable price using my limited skills. Fortunately, Google Maps offers a solution that I can use without having to become a AJAX/PHP/Javascript coder. The interactive map below shows sales data for zip code 20005. I emphasize interactive because you can click on an icon on the map below and its data will be displayed; you can move and pan the map, too, You do not have to leave this site.
The legend at right explains the colors used for each pin on the map. For example, a yellow pin on a square means the average price for the square is between $551,000 and $650,000. You'll get the exact data when you click the pin.
View Larger MapI'd appreciate feedback on whether using this type of map is helpful.