in three flavours (cf. López-Corredoira et al. 2008). The N- or S-like warps have $\omega_{\rm R}$ and $\omega_{\rm L}$ of the same sign, the signs of $\omega_{\rm R}$ and $\omega_{\rm L}$ for U-like warps differ, and L-like warps apply to galaxies in which only one side is warped. The difference between N- and S-like warps is unimportant from a physical point of view. However, we have retained this information because it is needed, for instance, when considering the orientation of warps in a cluster of galaxies (see, e.g., Battaner et al. 1991).

With this parameter we can, for example, objectively compare the appearance of a galaxy at several wavelengths to determine whether a colour gradient exists within the warp. We can also detect warps that would otherwise not have been found. Warps are not always completely symmetric, in which case this parameter would hide the information of the clearly warped side of the galaxy. To avoid this problem, we calculated the warp parameters on either side of our galaxies independently, along with $\alpha_{\rm s}$, the degree of asymmetry (Sánchez-Saavedra et al. 2003), $$\alpha_{\rm s} = \frac{| \omega_{\rm R} - \omega_{\rm L}
|}{\omega_{\rm R} + \omega_{\rm L}}.$$

One of the most 