Your text describes matching columns but your images and your example show matching rows. I'll assume you meant rows.
- Use readmatrix to read in your data since it appears that you are matching rows and your data appear to be homogenous, all numeric. You'll read in the two data sets as two separate matrix variables.
- It looks like your data do not have more than 7 decimal places so roundoff error shouldn't be a problem. If it turns out that your data are more decimal places that what appears in your screenshots, you'll need to decide how you deal with precision issues that may arise. Let's cross that bridge if we come to it.
This is where I get lost in your description. Are you asking whether the selected row of A exactly matches the selected row of B or are you asking whether both rows have the same values but perhaps in different orders? Or are you asking something else?
