If its not there, add a column to hold the percentage via table >maintenance>structure. For this discussion it will be called Percentage_Of_Total
Then a 2 part SQL. step one determine total area (I used square meters here, Mate) In SQL builder: Choose your polygon table in the table section replace the * in the first section with Sum(Area(obj, "sq m")) sq m can be replaced with other units MapBasic window shows: Select Sum(Area(obj, "sq m")) from MyTable into Selection Browse * From Selection the result will be one record giving the sum of the areas of all polys from your table. It is not necessary to Group By Objects. Note that the units of your existing individual area column and units of the query for total area must match. copy the figure returned above. I used an existing table of polygons I have and it returned 22956 for the sum of area(obj, "sq m"), we'll use that number in our next formula. then run an column update wizard (Table>Update Column): column to update is Percentage_Of_Total column you added above hit the assist button and build a formula to divide the individual object's area by the total area figure obtained in step one. The basic formula would then be Area (obj, "sq m") / total area. Notice that although you have a column for the individual objects' area, it is not necessary, the function Area() will return these figures without an actual column. So far, this procedure gives you decimals with no formatting for percentages, and MI has no Percent data type or functions. to get to a column of percentage, try this: Update MyTable Set Percentage_of_Total = Round((Area(obj, "sq m") / 22956)*100, .001) +" %" *100 converts the decimal to a percentage, it needs to be rounded to the nearest 1/1000th to be workable, and the + " %" concatenates the percent symbol into the figure, notice it is quote space % end quote to give a space between the numbers and the % sign. William "Woody" Woodruff Zoning Administrator Charter Township of Union, Isabella County, Michigan -84.80947000 43.61095100 2010 S Lincoln Rd, Mt. Pleasant, MI 48858 (989) 772 4600 EXT 41 Visit our web site at http://www.geocities.com/ctuzoning/index.htm -----Original Message----- From: Peter Hatton [mailto:[EMAIL PROTECTED] Sent: September 27, 2004 02:13 To: '[EMAIL PROTECTED]' Subject: MI-L PERCENTAGE QUERY Hi all, Can someone help me to do the following - I have a table of polygons with individual area totals for each polygon. Can someone tell me how I can determine the area percentage of each polygon for the combined total area ? Many thanks Peter Peter HATTON GIS Officer Greater Taree City Council PO Box 482 TAREE 2430 Ph 02 6592 5227 Fax 02 6592 5380 E-mail [EMAIL PROTECTED] This e-mail has been scanned for viruses by MCI's Internet Managed Scanning Services - powered by MessageLabs. For further information visit http://www.mci.com --------------------------------------------------------------------- List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] Message number: 13513 --------------------------------------------------------------------- List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] Message number: 13529
