iris.dat in Fuzzy Logic Toolbox does not have class information (name of the attribute). So, you need to add class information by yourself like:
setosa = iris((iris(:,5)==1),:); % data for setosa
versicolor = iris((iris(:,5)==2),:); % data for versicolor
virginica = iris((iris(:,5)==3),:); % data for virginica
If you have Statistics and Machine Learning Toolbox, use fisheriris instead.
load fisheriris
A variable meas contains features and Species is class information.
