14
W. K. Hardle, R. A. Moro, and D. Schafer
AR (SVM K5+K29+K7+K33+K18+K21+K24+K*)
Variable No.
Fig. 10. Accuracy ratios for SVM models with eight variables. Each model includes
variables K5, K29, K7, K33, K18, K21, K24 and one of the remaining. Box-plots are
estimated basing on 100 random subsamples.
6 Colour Coding of PDs
The RGB colour space is based on three primary colours, red, green and blue,
that are mixed to produce other ones. It is the colour coding scheme that is
used in monitors and TV. It is, however, inconvenient for colour coding since
we would like to make adjustments only to the channel responsible for colour
while keeping lightness and saturation constant. This can be achieved with
the HLS colour space.
We will represent the probability of default (PD) estimated with the SVM
as two-dimensional plots where each colour represents a specific PD. The PD
is a number that can be represented on a gray scale, e.g. in the RGB encoding
as (i, i, i) with i changing from 0 to 255, e.g. the colour R=255, G=0, B=0
corresponds to red, and R=255, G=0, B=255 to violet, etc..
The HLS stands for hue, lightness (or luminance) and saturation. By ad-
justing only hues and keeping luminance and saturation fixed we can generate
simulated colours from the range shown in Figure 14. The pure red colour
corresponds to H=0 or 360, the pure green to H =120 and the pure blue to
H=240.