iris.dat:
It appears this data file is included in Fuzzy Logic Toolbox for use in one of its examples, specifically this example. If you do not have Fuzzy Logic Toolbox installed, you will not have this data set installed.
fisheriris.mat:
Used by examples in Statistics and Machine Learning Toolbox, 14 different examples according to the search results. Again, if you do not have Statistics and Machine Learning Toolbox installed, you will not have this data set installed.
To see what products you have installed, use the ver function.
Broadening the search to examples in all products for the term "iris", it appears that Image Acquisition Toolbox and Neural Network Toolbox also have examples that use iris data. Since you or someone tagged this with the Neural Network Toolbox product, I suspect you want to run this example. That example uses the command x = iris_dataset; to read in its data.
