I'll start by admitting I am not familiar with this function, but based on what I can find in the documetnation, it appears you may not be using the correct syntax. First, lidarSLAM is part of the Navigation Toolbox, not the Robotics System Toolbox.
Also, note that MATLAB is case sensitive, so LidarSLAM and lidarSLAM are not the same thing. The function in MATLAB is lidarSLAM.
Based on the examples in that page, you would call it using one of the following syntaxes:
slamObj = lidarSLAM
slamObj = lidarSLAM(mapResolution,maxLidarRange)
slamObj = lidarSLAM(mapResolution,maxLidarRange,maxNumScans)
So I would expect your code to look like this
slamAlg = lidarSLAM(mapResolution, maxLidarRange);
