With FreeMat v3.6:
I obtained P_4_4.mat file for tutorial.
Tried to load it (either completely, or targeting specific variable). Get this error message.
"Error: unable to read data from file C:/BobR/study/FreeMat/P_4_4.mat - it may be corrupt, or FreeMat may not understand the format. See help load for more information. The specific error was: Not a valid MAT file"
Attached P_4_4.mat was obtained from York University site:
Used with "Labs for Signals and Systems: Using MatLab" (Stonick & Bradley: 1996)