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how_to_use_gbay [2018/12/13 14:50] – [3. Spatial inputs] stritihahow_to_use_gbay [2023/04/21 15:30] (current) – external edit 127.0.0.1
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 When the input data represents **hard evidence** (we know the state of the node at each pixel, with 100% certainty, e.g. we know that the land cover of a pixel is forest), then the input raster has one band, where the value of each pixel corresponds to the number of a state of the node. For continuous nodes, the value of the pixel represents the real value (e.g. forest cover of 75%).  When the input data represents **hard evidence** (we know the state of the node at each pixel, with 100% certainty, e.g. we know that the land cover of a pixel is forest), then the input raster has one band, where the value of each pixel corresponds to the number of a state of the node. For continuous nodes, the value of the pixel represents the real value (e.g. forest cover of 75%). 
  
-When we use **soft evidence** (a probability distribution for each pixel), the input raster should have as many bands as the number of states of the corresponding node. Each band represents the probability of a state (e.g. the probability that the land cover of a pixel is forest). The values of all bands should sum up to 100. +When we use **soft evidence** (a probability distribution for each pixel), the input raster should have as many bands as the number of states of the corresponding node. Each band represents the probability of a state (e.g. the probability that the land cover of a pixel is forest). The values of all bands should sum up to 100. 
 + 
 +If soft evidence is given (to a root or intermediate node), the effect is identical to the Netica's "calibrate..." function (in the "Enter findings" menu).  
 === 3.2 Vector === === 3.2 Vector ===
-When using vector data (**.shp** files or ESRI geodatabase files), the input nodes are represented in the attribute table of the dataset. +When using vector data (zipped **.shp** files or **.gdb** ESRI geodatabase files), the input nodes are represented in the attribute table of the dataset. 
  
-For **hard evidence**, the attribute table should have a column corresponding to the name of the input node, with values corresponding to the states of the node. +For **hard evidence**, the attribute table should have a column corresponding to the name of the input node, with values corresponding to the states of the node. A value of 0 means NODATA.
  
-For **soft evidence**, each state of the input node should be represented by a column of the attribute table, with values representing the probabilities of the states (which should sum up to 100). The column names should be the node name, followed by two underscores, an 's' (from state) and the number of the state. +For **soft evidence**, each state of the input node should be represented by a column of the attribute table, with values representing the probabilities of the states (which should sum up to 100). The column names should be the node name, followed by two underscores, an 's' (from state) and the number of the state. If all values are 0, it means NODATA.
  
 Example: to set soft evidence on node 'lu_t0', with three states, the attribute table should contain the columns:  Example: to set soft evidence on node 'lu_t0', with three states, the attribute table should contain the columns: 
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 ==== 4. Run the network ==== ==== 4. Run the network ====
  
-Once you have set up the network, selected the target nodes, and uploaded the spatial inputs, you can click on **“Run”** to run the network. gBay will use your spatial data to perform inference in the BN for each pixel or object, and produce an output of the results. +Once you have set up the network, selected the target nodes, and uploaded the spatial inputs, you can click on **“Run”** to run the network. gBay will use your spatial data to perform inference in the BN for each pixel or feature, and produce an output of the results. 
  
 Any potential **errors or warnings** will appear as pop-ups. If you want to see the progress of the processing, select the option to “Show console”.  Any potential **errors or warnings** will appear as pop-ups. If you want to see the progress of the processing, select the option to “Show console”. 
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 In addition, for each target node, some metrics of the posterior probability are calculated and stored in an additional raster file called target_node_stats.tif. For discrete target nodes, this file contains one band with Shannon’s evenness index of the posterior probability distribution: In addition, for each target node, some metrics of the posterior probability are calculated and stored in an additional raster file called target_node_stats.tif. For discrete target nodes, this file contains one band with Shannon’s evenness index of the posterior probability distribution:
  
-  J = H/Hmax, where H = i=1Npilog2pi , Hmax = log2(N), pi is the probability of state i and N is the number of states.  +\(J = H'/H_{max}\), where  \(H' =-sum_{i=1}^N(p_i*log_2p_i)\), \(H_{max} = log_2(N)\), \(p_i\) is the probability of state i and N is the number of states. 
 +(We use \(log_2\) to reflect the common use in information theory.) 
 + 
 The index is a standardized measure of entropy (can be compared between nodes with different numbers of states) and expresses uncertainty. It has values between 0 and 1, where 1 denotes a uniform distribution between all possible states (maximum uncertainty), and 0 denotes complete certainty that the output node is in a specific state.  The index is a standardized measure of entropy (can be compared between nodes with different numbers of states) and expresses uncertainty. It has values between 0 and 1, where 1 denotes a uniform distribution between all possible states (maximum uncertainty), and 0 denotes complete certainty that the output node is in a specific state. 
  
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  4. Standard deviation  4. Standard deviation
  
 +==== Overview of gBay spatial inputs and outputs ====
  
 +|         ^ **Input format**                                               ^ **Input values**                                                            ^ **Output**                                                        ^
 +^ Raster  | .tif file per input node                                       | **Hard evidence:**                                                          | **target.tif:**                                                   |
 +| :::     | :::                                                            | Value = node state (discrete nodes) or continuous value (continuous nodes)  | one band per state:                                               |
 +| :::     | :::                                                            | **Soft evidence:**                                                          | value = probability of state                                      |
 +| :::     | :::                                                            | One band per state                                                          | additional last band:                                             |
 +| :::     | :::                                                            | value = probability of state                                                | value = most likely state                                         |
 +| :::     | :::                                                            |                                                                             | **target_stats.tif**: bands:                                      |
 +| :::     | :::                                                            |                                                                             | 1. Evenness index                                                 |
 +| :::     | :::                                                            |                                                                             | Only for continuous nodes:                                        |
 +| :::     | :::                                                            |                                                                             | 2. Mean                                                           |
 +| :::     | :::                                                            |                                                                             | 3. Median                                                         |
 +| :::     | :::                                                            |                                                                             | 4. Standard deviation                                             |
 +^ Vector  | one .shp file or geodatabase .gdb (reads the attribute table)  | **Hard evidence:**                                                          | **Same geometry as input**                                        |
 +| :::     | :::                                                            | Column of attribute table with same name as input node                      | attribute table with a column for each state of the target node:  |
 +| :::     | :::                                                            | value = node state (discrete nodes) or continuous value (continuous nodes)  | value = probability of state                                      |
 +| :::     | :::                                                            | **Soft evidence:**                                                          | additional column:                                                |
 +| :::     | :::                                                            | Columns with node name and state number                                     | value = most likely state                                         |
 +| :::     | :::                                                            | (lu_t0__s1, lu_t0__s2, lu_t0__s3):                                          |                                                                   |
 +| :::     | :::                                                            | value = probability of state                                                |                                                                   |
how_to_use_gbay.1544709007.txt.gz · Last modified: 2023/04/21 15:30 (external edit)