===== Incorporating iterations into a model ===== ==== What will you learn? ==== * Iterations * Using Register Viewer * Functors: \\ - //[[:Repeat]]// \\ - //[[:Step]]// \\ - //[[:Extract Map Attributes]]// \\ - //[[:Load Categorical Map]]// \\ - //[[:Calculate Value]]// \\ - //[[:Mux Lookup Table]]// \\ - //[[:Set Lookup Table Value]]// Open the file ''brazilian_amazon_landscape.tif'' located in the folder lesson2 on the Map Viewer. Use "Amazon" as the current color palette. This is a land cover map of the Brazilian Amazon. The map has the following classes: 1 – Deforested (yellow)\\ 2 – Forest (green) \\ 3 – Non-forest (light brown) The intent of this exercise is to calculate the extent of remaining forest within each state. {{ :tutorial:brazilian_amazon_landscape.1.jpg |}} {{ :tutorial:inc._it._model_1.jpg|}} Begin placing one //[[:Load Map]]// and one //[[:Load Categorical Map]]// on the sketch. This latter functor will categorize a map if it is not categorized, i.e. cell values are identifiers to map classes, so when a map is loaded, it browses the map to identify all unique cell values that represent different categories or map classes, producing as a result a list of classes, which becomes embedded in the map header. Place one //[[:Calculate Map]]// and two //[[:Number Map]]// functors inside it.\\ \\ \\ Now assign a number to each //[[:Number Map]]// and then connect //[[:Load Map]]// and //[[:Load Categorical Map]]// to them.{{ :tutorial:inc._it._model_2.jpg |}} Load ''amazon_states.tif'' using the //[[:Load Categorical Map]]// and "Brazilian_amazon_landscape.tif" with //[[:Load Map]]//. Add a //[[:Number Value]]// from hook tool in the //[[:Calculate Map]]//, assign "1" to it and write the following equation: \\ \\ **if i1 = v1 and i2 = 2 then 1 else null** **TIP**: you can copy an equation from a text editor (using Ctrl+C) and paste it in the equation box (using Ctrl+V). A value is represented by v# (v1, v2, ..vn). Close the container. Do not forget to set the **Cell type** to "Unsigned 8 Bit Integer" and **Null Value** to "Use default value".{{ :tutorial:inc._it._model_3.jpg |}} {{ :tutorial:inc._it._model_4.jpg|}}Grab the container //[[:Repeat]]// from the Control tab and place it on the sketch. Drag //[[:Calculate Map]]// into it. It will automatically resize to envelop //[[:Calculate Map]]//. Then add the functor //[[:Step]]// into //[[:Repeat]]//. Open //[[:Calculate Map]]// by clicking on its top left icon and connect //[[:Step]]// to **Value** port of //[[:Number Value]]//. Open //[[:Repeat]]// with the Edit Functor tool and insert "9". {{:tutorial:inc._it._model_5.jpg?300 |}} \\ \\ \\ \\ \\ \\ \\ This implies that the model will iterate 9 times. The //[[:Step]]// functor self-associates to the enveloping container and passes to //[[:Calculate Map]]// the current step. Thus for each iteration //[[:Calculate Map]]// produces a map containing the remaining forest (value 2) for each state. Now you need to sum all cells that represent forest. Note that the output is a binary map with only ones and nulls, the latter is represented by zero. Next, use //[[:Extract Map Attributes]]// (Map Algebra tab) to extract the sum of non-null cells. This functor produces as output a table with [[:extract_map_attributes#Notes|these map attributes]].{{ :tutorial:inc._it._model_6.jpg |}} The area extent is the sum of non-null cells (field 9) multiplied by the cell area in hectares (field 7). You need to add one //[[:Calculate Value]]//, located in the Table tab, to perform this calculation. Also, select one //[[:Number Table]]// clicking in Create a hook (magnet icon) inside functor action bar, which will receive the attribute table output from //[[:Extract Map Attributes]]//. You need to enter "1" to assign an identifier for this table. Finally, write:\\ **t1[7]*t1[9]**\\ (cell area (in hectares) * sum of the values (excluding null cells)) **TIP**: You can replace the\\ \\ **t1[7] * t1[9]**\\ \\ expression with\\ \\ **t1["cellArea"] * t1["nonNullCells"]**\\ \\ All the attributes produced by //[[:Extract Map Attributes]]// and //[[:Extract Lookup Table Attributes]]// can be replaced by the corresponding attribute predefined names. See //[[:extract_map_attributes#basic_attributes|Extract Map Attributes]]// and //[[:extract_lookup_table_attributes#basic_attributes|Extract Lookup Tables Attributes]]// for a list of predefined attributes names. Note that **t1** means table #1. In this case, the brackets are needed to represent the value associated to a table key. {{ :tutorial:inc._it._model_7.jpg |}} {{ :tutorial:inc._it._model_8.2.jpg |}}\\ \\ Now you need to fill in a table in order to store the area calculated for each state. The functor [[:set_lookup_table_value|Set Lookup Table Value]] updates a lookup table placing a value to a position defined by a key. To fill in the entire lookup table, you need to develop a loop that enables this functor to browse through the lookup table. To close this loop, you will need a functor that is key to the development of dynamic models. Here we introduce the concept of Mux functor. A //Mux// functor can be a map, a categorical map, a lookup table, a table or a value. Look at the Control tab to find //[[:Mux Lookup Table]]// and drag it into //[[:Repeat]]//. Also drag //[[:Set Lookup Table Value]]// from the Lookup Table tab. {{ :tutorial:inc._it._model_9.jpg |}} Now, click on the //[[:Mux Lookup Table]]// with the Edit Functor Ports. Every Mux functor has two input ports. In the first iteration, it reads the input from the **Initial** port; thereafter it receives the data from the model step through the port **Feedback**. This process allows data to be updated by the model, thus becoming dynamic. Hence this functor is key to the incorporation of feedback into a dynamic model. Also open //[[:Set Lookup Table Value]]// with the Edit Functor Ports. This functor receives a table that will be updated with a value placed in a position defined by a key. So you need to connect table output from the functor //[[:Mux Lookup table]]// to the input port of //[[:Set Lookup Table Value]]//. Again, let’s connect the output from //[[:Set Lookup Table Value]]// to //[[:Mux Lookup Table]]//. When a connection has two or more options, the Edit Functor Ports window opens automatically. You have to choose the port **Feedback**. {{ :tutorial:inc._it._model_11.jpg |}} {{ :tutorial:inc._it._model_12.jpg|}}\\ \\ \\ Now click on the port **Initial** with the right mouse button. You will open a table editor. In this case you just need to enter “0" and "0” as **Key** and **Value** for the first table record, and then save these inputs using the "+" button.\\ \\ \\ \\ \\ Still, you need to connect the output from //[[:Calculate Value]]// to the **input** port of //[[:Set Lookup Table Value]]//. \\ {{:tutorial:inc._it._model_13.jpg|}}\\ The Edit Functor Ports window pops up because there are two options. Connect the arrow to the port **Value**; the **key** comes from the current model step via the connection of //[[:Step]]// to //[[:Set Lookup Table Value]]//. {{ :tutorial:inc._it._model_14.jpg|}} \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ \\ Click on the layout tool Left to Right and your model will look like the one below.\\ \\ {{ :tutorial:inc._it._model_15.jpg |}} Observe that the **feedback** connection is between //[[:Mux Lookup Table]]// and //[[:Set Lookup Table Value]]//. As a last step, you need to save the lookup table into a file. Drag the functor //[[:Save Lookup Table]]// from the Input/Output tab. Connect //[[:Set Lookup Table Value]]// to it and edit the name for the CSV file. Although **Suffix Digits** is "2" by default, the file name won’t have a suffix because it will be saved after //[[:Repeat]]// is done. **TIP**: If //[[:Save Map]]// is placed inside //[[:Repeat]]//, it will save a file per time step and a digit representing the time step will be added to the end of the file name. {{ :tutorial:inc._it._model_16.jpg |}} Save it and if everything is O.K., click on the run button. This may take a short while. {{ :tutorial:inc._it._model_17.jpg |}} Go to //[[:Set Lookup Table Value]]//, open inspect functor into functor action bar and click to inspect the output port **Updated Table** and run the model again to view the result. Also make a chart clicking on the chart button (bottom left). {{:tutorial:inc._it._model_19.jpg|}}{{:tutorial:inc._it._model_19_2.jpg|}} These are the areal extents of the remaining Amazon forest in hectares per state. **TIP**: You can also open the CSV file with a spreadsheet program. __You have successfully completed the two introductory lessons__. Another way to solve the query of this lesson is through the use of a subset of Region functors. This will be the topic of the next lesson. [[tutorial:using_the_concept_of_region|Next lesson]]