Reciprocal of the sum of the reciprocals of conductance values in Transition* objects
Description
Reciprocal of the sum of the reciprocals of conductance Transition* objects
Usage
1  sumReciprocal(x1, x2)

Arguments
x1 

x2 

Details
To calculate the total resistance of two resistors that are serially connected, we should add their resistance values. However, if we work with conductance values, we need to take the reciprocal of the summed reciprocals of the conductance values. This function does that when adding two TransitionLayers with conductance values (matrixValues(tr) == "conductance"
).
For a TransitionLayer with resistance values (matrixValues(tr) == "resistance"
), the function will not take reciprocals for that object, but will still take a reciprocal for the final product (which will consequently have conductance values).
Value
TransitionLayer object containing conductance values.
Author(s)
Jacob van Etten jacobvanetten@yahoo.com
Examples
1 2 3 4 5 6 7 8 9 10 11 12 13 14  #Create a new raster and set all its values to unity.
raster < raster(nrows=18, ncols=36)
raster < setValues(raster,rep(1,ncell(raster)))
#Create TransitionLayer objects
tr1 < transition(raster,mean,4)
tr2 < tr1
matrixValues(tr1)
#Set one to resistance
matrixValues(tr2) < "resistance"
#Sum the two objects
sumReciprocal(tr1,tr2)
