I need one help. i am using arcgis 10. I actually want to show to create a buffer of a single point. But, the radius of that buffer depends on a simple formula (say Radius = a*b*c) instead of entering directly the radius, is there are way to just enter the constants on the model builder, use the result and connect it to buffer so that we can get that answer? Thanks hope everyone understood my question.
Sure, it's fairly straightforward, but you may do well to read this Creating Tools With ModelBuilder link:
You might also check this link on Calculate Value in ModelBuilder: http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//004000000004000000.htm
1)Open ModelBuilder and add your feature class/shapefile and your buffer tool.
2) Add the "Calculate Value" ModelBuilder function (Accessed by right clicking the model area and selecting Model Only Tools>Calculate Values).
3) Add 3 (or however many you please) variables to your model (Insert>Create Variable) of a data type appropriate for your operation. Name these something easy and appropriate (e.g. A,B,C).
4) Right-click these variables and enable "Model Parameter".
5) Open the Calculate Value tool and set its expression to whatever you'd like using the variables encased in % %, as such: %A% * %B% * %C% (this will be the product of A*B*C).
6) Connect the Calculate Value tool to the Buffer tool as the Distance unit.