Calculate the average in a field evaluator

Discussion created by ld on Jul 21, 2011
Latest reply on Jul 25, 2011 by ld

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Hello,
I have a street network with the average slope for each street segment in a column. Now I want to use this column to calculate the average slope per route. Thus I think would like calculate the average of the slope column in the field evaluator. Is that possible?

I tried already to put the value = Avg (???slopecolumn???) but it didn´t work.

Thank you in advance,
Lisa

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jsandhu-esristaff Jul 21, 2011 7:44 AM
Lisa,
The route solver returns one line feature. What you need to do is select all the lines from your street feature class that were covered by the route and then open the attribute table, click on the slope column to make it active and then right-click to bring up the menu and choose Statistics. It will report back among other things, the mean of the slope. You can also look at the GP tool Summary Statistics.
Jay Sandhu
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ld Jul 23, 2011 6:20 AM
Hello Jay,
the problem is that I have 2000 routes and cannot calculate for each route the average slope by hand. So I though there might be a way to calculate the average with a little syntax in the network as an evaluator, insted of adding all values (like it does with minutes) it could give the average. Or is that not possible? Can I use the slope then somehow else in the network?

Lisa
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jsandhu-esristaff Jul 24, 2011 2:32 PM
Perhaps you can be more clear in what is your end goal...

if the goal is for each route to compute average slope AND you are defining the average slope to be the sum of the slopes for each edge divided by the number of edges in the route THEN do the following:

Add two more impedances to your network dataset called EDGESLOPE and EDGECOUNT. Set the evaluator for the EDGESLOPE to load from the average slope on each edge. Set the evaluator of the EDGECOUNT to a constant 1. Now when you solve for the routes, set the route layer properties to accumulate the EDGESLOPE and EDGECOUNT. After the solve, each route will have the total slope and number of edges. Add one more field to the output route layer called AverageSlope and use the field calculator to simply divide the accumulated edgeslope and edgecount fields.

Jay Sandhu
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ld Jul 25, 2011 1:56 AM
Thank you Jay!

That is a good idea. I thought the so calculated average is an easy solution. I am aware of the fact that then all values are positive and don´t represent the real up or down slope. Do you have other suggestions how to calculate the overridden slope per route? I have a .dem file in 25m resolution thus I could calculate it more precise I guess.

Lisa
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