Today, we're going to spend some time talking about the interface tab in NetLogo and primarily how you can design a good interface for your model. So here we're looking at the NetLogo 'Fire' model... which you probably remember from the beginning of the course, and you'll notice right away when you look at the interface tab that there are two buttons that almost always appear on every interface in the NetLogo models library. That's the setup button and the go button. In the next set of lectures, when we talk about how you write your code, we'll explain that these are basically the standard way in NetLogo - - again NetLogo style not syntax - of controlling the model run. So you almost always have a setup command to initialise the model and a go command that allows the model to run. And to do that, you'll see these buttons here, And to create them, you just go up and you select 'button', hit 'add', click someplace, and you can type in the command that you want that button to execute. You can also give it your own display command as well, like 'my setup', or something like that. And this will then execute the code. So 'setup' now executes the same code as this 'my setup', even though the name of it is different. And then you can always edit or delete by right-clicking or control-clicking... and then you can either select it and move it around... you can edit it again if you want to change what it says... or you can just delete it. So that's buttons. In fact, there are a number of different interface elements you can automatically create in NetLogo... buttons being one of them. There are two others here in the NetLogo 'Fire' model... the slider, which allows you to specify a particular value for a global variable, and a monitor, which allows NetLogo to present results back to you in terms of what's going on. Let's talk about those. The slider in this case controls the density of the trees in the world and if you right-click on it you can see that it has a property of having a minimum value, an increment, a maximum value, a value at the initial start of a run and units, this is just what displays right here, so you could say 'percentage trees'. You can also make the slider vertical if you want, as opposed to horizontal, and then this is the name, the name of the global variable that the slider controls. Now for the monitor, if you right-click on it, you'll see that it is actually a piece of code, and what it's doing is taking the variable 'burned-trees', the number of burned trees... dividing it by the number of initial-trees, and multiplying by a hundred... to get the percentage that are burned trees. And then you can specify the display name, how many decimal places are displayed... and what size to put it in. So there are three of the elements. And if you look up here again you'll notice... that there is one element which is purple, which is buttons because they are directly interacting with the model run. There are four that are green: these are things that control inputs to the model. And then there's three more that are tan, and one that's a kind of white. The tan ones are ones that allow NetLogo to output results. And the white one, note, is just a predefined note that you can place anywhere, so you can describe things, for instance, 'this is my note', just to illustrate and document the model. So the 'Fire' model has a slider, a button and a monitor. Another interesting model to look at would be the 'Segregation' model. So if we go to 'Social Science' and load up the 'Segregation' model we've previously looked at... You'll see this has sliders and buttons, and again has a setup and go. You'll also notice that the go is greyed out, and won't turn regular until after you've hit setup. This is because you can disable the button until 'ticks' start, which we'll talk about in the next couple of days. But besides these, there are also some other interesting things here. There is a plot, which is plotting results, There are monitors as well, as we saw before. And then there is a chooser that allows you to choose particular values... So this chooser actually lets you choose whether the visualisation is the classic turtles or the new square 'X', so you can choose which one you want. Finally, I wanted to show you one other, which is the 'Voting' model, because the 'Voting' model uses the last simple type of input to the model which we often see, which is the boolean switch. The boolean switch controls whether a variable is true or false. So in this case, we are looking at a model of votes where people look at their neighbours... to decide which colour to be, blue or green, based upon what their friends are. And these boolean switches allows you to change their behaviour. So this one allows you to say 'they should change their vote if there's an equal number of people tied' and this one says 'if it's a close call, for instance, if it's 5 to 3 one way of the other... they should change their vote' And if you look at these, all you're specifying is the name of the global variable, and all global variables that have booleans in NetLogo always end in a question mark ('?') and so you'll always see that in that particular context. And then these variables can be accessed directly within the NetLogo code... which, as I mentioned, we'll talk about in a little bit. There are a couple of other things we didn't mention... we didn't mention text input, that's a little more complex, you can look that up in the NetLogo manual. output, this is a textual output, that you can also look up and explore on your own. But the main ones you're going to use are probably button, slider, switch, chooser and then monitors and plots. We'll get into more detail about how to build the plots, because they're a little more complex, in a future lesson. There's a couple of last elements I want to talk about about the interface tab. One of them, you may have played around with a little bit before, is the speed slider. It's this little slider up here that allows you to control the speed of the models. So we hit 'setup' and then what we can do, if we want to see the model run a little slower, is we can move it down, and then what will happen is that the updates of the graphical image... of the model are going to happen at a slower speed, And, if we want, we can speed up the model, and allow it to run faster. And if we move it all the way up, what happens is we see very few of the actual updates, and so we just see, in this case, the end results. And if we make the model a little denser, then we see one interim picture before the final results. You can tell NetLogo whether you only want to view the updates on 'ticks' or 'continuous', And essentially the speed slider is allowing you to vary how quickly you're seeing those updates. It's a useful tool especially when you're debugging, to play around with the speed slider The other thing I want to discuss with regards to the interface is the world properties tab or the model settings tab. It's found by right-clicking on the background of the model... or you can click the 'Settings' button up here... And this allows you to control the dimensions of your world first and foremost... So, in the 'Fire' case, we've set the middle of the world to be '0, 0' with the boundaries being the appropriate ones away from that, so the max coordinate is 125. But you can, for instance, move the centre of the world - the '0, 0' coordinate - to a corner, for instance the bottom left, which is standard looking at the first quadrant of most Cartesian graphs You could put it at an edge, so now it's in the middle at the bottom, or you can actually set the location of the centre of the world to any place you want, just by telling it what you want the minimum and maximum pxcor and pycor to be. min-pxcor, max-pxcor, min-pycor and max-pycor, which we'll explain in the next set of lectures... are the minimum and maximum patch x and y coordinates. One other thing you'll see here, say you want a bigger world You want more trees, to see if the results depend upon the size of the world. We can, for instance, change the max-pxcor and max-pycor to something much bigger... but when we do that, you can see it's now exploded beyond the size that you can see here. One way we can fix that is - you see the patch size was set to '2' - If I set it back to '1' it will at least bring some of it back into view. The patch size parameter controls how many pixels each patch is the size of. We'll talk more about patches in the next couple of days. Besides that, we can also control the font size, which is the size of the different characters, the frame rate, how many frames we'll see, And whether we show the tick counter, which we'll talk about in the next couple of days, and how the tick counter is actually labelled. So in the 'Fire' model if each timestep is roughly an hour... we can actually change it to 'hours' as opposed to 'ticks'. There's one last element of the model settings I wanted to discuss and that is these wrapping buttons. To explore these, I brought up the 'Flocking' model. What I want you to notice is that, if you run the 'Flocking' model, if you watch carefully, any birds that fly off one side of the screen appear on the other side. This is sometimes called the 'pacman' world, because as pacman goes off one side he comes back on the other, and we call this 'world wrapping' in NetLogo. You can make this very clear, if I pause the model, and I go up here... and I watch this turtle right here... it will highlight a little grey circle around... and now as you can see, as that particular bird moves across the world... we can see that it just went off one side and appeared on the other. That is because we have world wrapping on, so the world wraps horizontally and vertically. If we turn world wrapping off, what you'll see will be very interesting... in the flocking model what happens is that the birds fly to the edges of the world... and just get stuck there. And that's because at that point, they no longer have any rules as to what to do... and once they get stuck at the edge of the world then NetLogo won't allow them to go past. So this is another thing to consider. On some models you want to have world wrapping on, in some models you don't what to have it on And you can make the decision as you chose. And, by the way, you can also have it only on for part of the world... either horizontally or vertically. So in this case I've turned it on just horizontally so the birds can move this across the left and right edges, they can't move across the top or bottom. So that's it for the interface tab. In the next set of discussions we're going to be talking about the code tab.