getMapData

Create Lookup Tables

Generate a full lookup table of values that map the probability values to the minimum and maximum limits of int16 values.

Create an array of int16 values from intmin to intmax. Define the probability limits.

intType = 'int16';
intLinSpace = intmin(intType):intmax(intType);
numOfPoints = length(intLinSpace);
probLimits = [0.001 0.999];

The exampleHelperProbToLogodds and examplerHelperLogoddsToProb functions convert between the log-odds and probability values. Use the helper functions to get the log-odds limits and generate the array for looking up log-odds values. Create an interpolated grid for the entire lookup table.

logOddsLimits = exampleHelperProbToLogodds([0.001 0.999]);
logOddsLookup = single(exampleHelperLogoddsToProb(linspace(logOddsLimits(1),logOddsLimits(2),numOfPoints)));
interpTable = griddedInterpolant(logOddsLookup,single(intLinSpace),'nearest');

Specify Transform Function Handles

The transform function handles utilize example helpers that define how to convert between log-odds integer values and the probability values with an applied saturation limit. The probability saturation limits are [0.001 .999] as previously specified. This behavior is similar to the occupancyMap object.

getXformFcn = @(obj,logodds,varargin)...
    exampleHelperIntLogoddsToProb(logodds,logOddsLookup(:),intLinSpace);

setXformFcn = @(obj,prob,varargin)...
    exampleHelperProbToIntLogodds(prob,interpTable,logOddsLookup(:),intLinSpace,probLimits);

Create Map Layer

Generate an occupancy map layer object from a matrix of probability values. Specify the get and set transform functions.

occupancyLayer = mapLayer(repmat(0.5,10,10),...
                           'LayerName','Occupancy',...
                           'GetTransformFcn',getXformFcn,...
                           'SetTransformFcn',setXformFcn);

Notice that when you create the map, the default value is 0.001 instead of 0. This difference is because the SetTransformFcn function has been applied to the default value of 0 when you create the object, which saturates the value to 0.001.

disp(occupancyLayer.DefaultValue)

    0.0010

Get and Set Map Data

The map data matches the matrix you set on creation.

extData = getMapData(occupancyLayer) 

extData = 10×10

    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000
    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000
    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000
    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000
    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000
    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000
    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000
    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000
    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000
    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000    0.5000

Set specific map locations to values that are:

setMapData(occupancyLayer,[0 0],0.00001)
setMapData(occupancyLayer,[5 5],0.25999)

For the first location, the probability is bound to the saturation limits.

extData = getMapData(occupancyLayer,[0 0])

extData = 
0.0010

The second location returns the value closest to the probability value in the lookup table.

extData2 = getMapData(occupancyLayer,[5 5])

extData2 = 
0.2600

The generated map layer can now be used for updating a probability occupancy map that are stored as int16 values. To combine this map with other layers or map types, see the multiLayerMap object.