result[mask] = op(xrav[mask], y) TypeError: unsupported operand type(s) for -: 'str' and 'str'

This error message indicates that you are trying to perform a mathematical operation (subtraction) on two string values. Python does not allow mathematical operations between strings.

To resolve this error, you need to make sure that the values being operated on are numeric values, such as integers or floats. You can convert the string values to numeric values using the `int()` or `float()` functions, depending on the type of numbers you are working with.

For example, if `xrav` and `y` are supposed to be numeric values but are currently strings, you can convert them like this:

xrav = float(xrav)
y = int(y)

Then, you can perform the subtraction operation between `xrav` and `y` without encountering a type error.