though is the third in a series of tutorials around how to use iterators in model builder be slightly different format than the two that preceded it in which I demonstrated a model and then we built it together this one is just gonna walk through three models that I've built and also what we're gonna be working on this one is something that might seem like it's a little bit more basic than the other two and it certainly is in the beginning but I'm choosing it as the third video because this is a concept that we can use to piggyback into something way more you know radical is the wrong word till I get excited about mark and GIS but at least downright interesting and one of the things that really allows you to do some neat analysis with model builder kind of takes root in this concept and it's this idea of for alright so in previous tutorials we went through these ones down here to say okay I have 25 feature classes and I need to run through them and do the same thing or maybe something slightly different to each check and we're not gonna have a video tutorial on this but the idea for these field value you know if you have a series of values that you're storing at a table and you want to pass those through to another tool you can go through each one and pass them through multi-value if you have multiple things stored in multiple different data sets feature selection row selection that's a totally new you know kind of concept here totally different than these two this one's saying give me a single shape file or a single table and I'll go through each component part very very new and so when I end with this one you're gonna say that's a little boring you know cuz all four really does drag it in to show you is it's really just saying hey give me some inputs from value 1 to value whatever right so essentially what you're just setting up here is ya you're allowing some values to be passed if you want but really what you're doing is preparing rounds right go through something four times and you know as they started this video that does seem pretty basic and the first example I'm gonna show treats a deception but this tool I'm gonna use to introduce a pretty cool concept that takes its route here something that's called feedback variable and we'll see what that is in a couple of steps but at our first example here I've got East Falls little neighborhood created one called for easy and it's a pretty simple tool here and I start with four I'm going from value 1000 to value 3000 by iteration iterative a thousand right so I'm iterating three times 1000 2000 3000 but I'm using values and as you can see through my connection those values are actually getting passed directly into the buffer right so I'm using East Falls and look at that my linear unit is shut down right it's not even hopping out because that's what I picked from my linear unit I literally connected value here and said that it was the distance so what's gonna happen is three times through this tool is gonna run it's gonna buffer 2,000 feet then 2,000 feet then 3000 feet remember from previous videos when I in case something in percent I'm a same take on whatever that value so what you're gonna see here is it's gonna come back saying east falls writer EF 1000 2000 3000 and I can even make that a little bit easier to understand I even go in here and say why don't we just make that EF buffer okay so we can fully remind ourselves and East Falls and buffering and I'm doing it by a certain value all right save it run it one and two and three super simple tool and I'm gonna actually save this and get out of it cuz sometimes it messes up my ability to to render graphics here zoom out alright 1000 2000 we started with East Falls alright so let's just look it out I started in East Falls and there we go I buffered its edge at a thousand feet right and then I went the next round and I said hey buffer East falls by two thousand feet and then furries Falls by 3,000 feet super simple right that's the basic concept of a for next round let's do it a little bit more complicated I make a good group layer here that says for easy so I can store those if I want to use them again and another one that was a little bit more complex now this looks almost identical if I open the two there is however a critical difference so they both start out the same all right for all right between 1,000 and 3,000 one my easy one now 1000 and 3000 storing that value passing it through to the buffer all right the same thing here with the buffer but notice what happens here is I'm actually taking this buffer and I'm passing it back in to the tool I'm creating here what's called a feedback loop I mean let's wrap our heads around this for a moment I'm gonna take something I'm gonna buffer by a thousand feet and then I'm actually gonna take that buffer and I'm gonna replace East Falls with it so the next time this tool runs it's not gonna buffer on East Falls it's gonna buffer on the old buffer and then it's gonna buffer on that buffer and then it's gonna buffer on that buffer what we're doing here is taking an output ten things down the road and passing it back in is the new input let's see how it actually plays out in action one and two and three starting to look a little bit different and we'll see exactly even why let's get it set up in a way that it's easy to see all right before I even run through this again oops and I'm gonna save both of these just because it's a little hard to be able to render like I said it was having some issues alright so when I did the first one easy right oops Apple Mouse totally get it right you buffered on the outside only at a thousand feet very easy to wrap our heads around then you buffered at the outside only for two thousand feet very easy to wrap our heads around and finally three thousand three totally fine totally easy to wrap our heads around let's do the complex starts out the same but then remember what happens here is now this output this outer buffer here becomes the new thing that's gonna get buffered at 2,000 feet what is a 2,000 foot buffer where you're only going on the outside look like here well it looks like this 200 feet on the outside 200 feet we think of this as an inside but it simply just means right go from the edge outward instead of coming in 2,000 feet that way and that's the new shape weekend and now this shape is gonna pass itself back in and be buffered at 3000 feet and what is a 3000 foot buffer on this look like it gets even kookier it comes out here and then it goes in here and it ends up looking something like that so what we've done here whoops oh dear taking its time really it's done what's called feedback loop all right so we're essentially taking an output and using it as another input and I've got on one more example that that I call or I thought I called Swiss cheese and the reason it's called Swiss cheese hopefully you'll see in a second and I've got something here notice I'm not attaching the for I'm not using the value here the for simply exists to say I'm going from value 1 to value 5 and I'm going in iterations of one it's a one and then two and then three and then four and then five in each time each time each time I'm doing the same process I'm gonna pass one random pointer I'm gonna create a random point and I'm gonna create that random point using East Falls as a boundary I'm gonna buffer from that point and then I'm gonna erase it all right now let's actually look at what the outcome looks like here before we get too deep into this tool so I'm gonna run this one 1 & 2 & 3 & 4 & 5 and so on and so forth essentially here's what I've done with this the process that I was setting up here what if you had to site things randomly right so imagine you're uh you know let's say oops let me make sure this gets deleted so that we can actually see everything okay so let's pretend that you have to cite something here and then I don't know you're an artist we'll say for the purposes of this assignment and you need to cite something randomly where you gonna do like your next mural or an exhibit in East Falls and see you cite something randomly here good that happened in year 1 excellent and eventually in year 2 your gonna cite another installation but you say to yourself well look I don't want to have something where I you know keep citing everything right around the same area here maybe I want to make it so that in year two nothing within a thousand feet of this is eligible and that's really what I did here if you want to run back to this tool I created a random point and then I buffered a thousand feet from that random point and then I used that thousand foot buffer to erase and a thousand foot boundary in East falls so that now in year two this would be the area that's eligible and then I cited another point buffer that by a thousand feet and then this is what would be eligible in year three and that's happening because I am replacing East Falls each time I am buffering and then cutting a hole with that buffer in what used to be East Falls and passing that back through so now when the random points gets generated it's only allowed to use the you know slightly smaller version of East Falls that's you know iteratively getting erased and then I cite a third one and and as you can see each time there's been a site sighting there's an a thousand foot buffer that gets cut out in each subsequent round until we finally get to whatever the fifth area of eligibility would be right when all of those areas would be cut out so for a fascinating kind of concept here and the way you were able to create a feedback variable as I just did here is you simply take something and drag it to connect as an input to something else another way you're able to do it is if you actually double-click that input oh my apologies if you right-click that input and go to properties you can select what's called a feedback variable here and remind it hey your feedback you're supposed to take right here eligible value as a feedback that's essentially you're coming in and you're gonna be you know what replaces the old value with your new self and just pause for a moment we on this video and really think how cool this is as a concept I mean imagine you're modeling and I'm doing a silly example here that I set up really quick to demonstrate the tool but imagine you're you know trying to predict development codes in an area and maybe you need to take into consideration your development codes over multiple years that you know for every new development that comes in the landscape is gonna change differently and so whatever rules you design in year two whatever happened in year one almost has to pass back into the tool for year two you know an example I used in one of my classes is imagine you have to site bike share stations and you can build a whole algorithm to help you pick out the best areas you know maybe places where there's you know a good relationship between where people work and where they live you can preface you know certain very busy streets are areas where the populations dance or around cultural sites so on and so forth but if you're building a program that sites like stations as an example over multiple years you must realize that in year two you're gonna have considerations that you didn't have in year one namely you might have the bike stations that you cited in year one and maybe you don't want new bike stations to be near them right or you don't want too many in an area so suddenly you have a variable that you didn't have the first time you did an iteration and this is what allows you to repass that back into the tool knowing that it's gonna be used in the second iteration a super cool and interesting concept around how you use what are called feedback variables
