What I am trying to do?
I want to explore the relationship between Magnetic Field and Blood Pressure in case of diabetic patients. In short, I will create a heavy magnetic field and will collect magnetic field's value on three different axes. After data collection, I want to correlate blood pressure with magnetic field's values in three different axes (e.g. magnetic field in x axis).
Then, what is the problem?
As magnetic field is a vector, values of magnetic field in each axis can be positive as well as negative. However, in case of magnetic field,
..... scientists and engineers use the terms ‘positive’ or ‘negative’ instead of ‘North’ or ‘South’. The positive pole is considered the North-seeking pole. 
Therefore, positive or negative magnetic field in the axes do not mean lower or higher values. Rather, positive magnetic field indicates a direction and negative magnetic field indicates the opposite direction. Consequently, if we set these negative values, I think, it will misinterpret the correlation between blood pressure and magnetic field.
Therefore, my question
Shouldn't we take absolute values when positive or negative sign indicates only direction, not higher or lower values?
Sample Data (Randomly Generated)