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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>Hi all,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I’m working with parcel data from several different regional sources. In some cases, the parcel data comes with a households field, in others with a dwelling units field (in rare cases, both). In all cases, I need both. Luckily, either can be calculated from the other using census multipliers.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><span style='mso-list:Ignore'>1.<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>What is the best way to add the missing column when it does not exist?<o:p></o:p></p><p class=MsoListParagraph><o:p> </o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><span style='mso-list:Ignore'>2.<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>Then, how should I go about populating the newly created field using a calculation based on the other field (keeping in mind that I don’t want to overwrite either field in the case that both existed in the input data)?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Ideally, I would be able to add the missing field in cases where it does not exist and populate its rows using a calculation based on the existing field. Because this step must nest in a larger set of processes, it is impractical to check manually each time a new input goes through. I’ve seen a good deal of discussion of this topic on forums but haven’t seen any clear solutions.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Thanks, <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Century Gothic","sans-serif";color:gray'>Conor Henley<o:p></o:p></span></b></p><p class=MsoNormal><span style='font-size:7.5pt;font-family:"Century Gothic","sans-serif";color:gray'>GIS/Regional Planning Intern<o:p></o:p></span></p><p class=MsoNormal><b><span style='font-size:7.5pt;font-family:"Century Gothic","sans-serif";color:gray'><o:p> </o:p></span></b></p><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Century Gothic","sans-serif";color:#CC6600'>C A L T H O R P E</span></b><b><span style='font-size:10.0pt;font-family:"Century Gothic","sans-serif";color:gray'> A S S O C I A T E S</span></b><b><span style='font-size:7.5pt;font-family:"Century Gothic","sans-serif";color:gray'><o:p></o:p></span></b></p><p class=MsoNormal><span style='font-size:7.5pt;font-family:"Century Gothic","sans-serif";color:gray'>2095 ROSE STREET, SUITE 201, BERKELEY, CALIFORNIA, 94709 USA<br>510-548-6800 | 510 548-6848 (fax)<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:7.5pt;font-family:"Century Gothic","sans-serif";color:gray'><a href="mailto:sheara@calthorpe.com"><span style='color:blue'>conor@calthorpe.com</span></a> | <a href="www.calthorpe.com"><span style='color:blue'>www.calthorpe.com</span></a><o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>