1. You most likely have a variable named std. This command should give you that information (copy-paste it to the Command Window and run it):
which std -all
If you have a Windows computer, all those results should be in the C:\Program Files\MATLAB\... directories, and none in your user files or as variables.
2. The std function takes the standard deviation across the columns (or rows) of an array, producing one value for each column (or row). The std2 function takes the standard deviation of all the elements in the array, as though they were all a single vector.
