Numpy array mask using values from successive rows, in one line

Question

I'd like to make a numpy mask to select only rows from an array where a value from one column in a row is equal to the value in the same column from the next row.

Yes, the mask is easy to do with a for loop, but I'd like to know if there's some on-line python syntax I can use, the idea being something like this:

data=SomeNumpyArray
filtered=data[(data[thisRowAndColumn] == data[nextRowAndSameColumn])]

This seems like the sort of thing that can probably be done with numpy in one line. Copy the array but shift it up and make the comparison, or something?