What is the cartesian sign convention used for spherical mirrors ?

Explanation

i. The pole of the mirror is considered as origin and all the distances are measured from the pole.
ii. Principal axis is taken as X-axis and all the distances parallel to the principal axis are measured from the pole of the mirror.
iii. The object is always kept on the left of the mirror.
iv. All the distances measured to the right of the origin (in the same direction of the incident ray) are taken as positive, while those measured to the left side of the origin are taken as negative. Thus, the focal length of a concave mirror is negative while that of a convex mirror is positive.
v. All the distances measured vertically upwards from the principal axis are taken as positive and those measured in vertically downward direction, are taken as negative.