各位大虾好！小弟初学R中的投影寻踪回归PPR，对于结构如何解读有点犯难。有关投影寻踪的书我看的是《投影寻踪模型原理及其应用》，书中ppr的应用章节给出的案例，其结果有预测值，以及a和c两个参数值。而R软件中的ppr说明中的范例的结果是3个因变量的term1和term2的值，这个要怎么对应到书上的内容？谢谢！
Examples
require(graphics)
# Note: your numerical values may differ
attach(rock)
area1 <- area/10000; peri1 <- peri/10000
rock.ppr <- ppr(log(perm) ~ area1 + peri1 + shape,
data = rock, nterms = 2, max.terms = 5)
rock.ppr
# Call:
# ppr.formula(formula = log(perm) ~ area1 + peri1 + shape, data = rock,
# nterms = 2, max.terms = 5)
#
# Goodness of fit:
# 2 terms 3 terms 4 terms 5 terms
# 8.737806 5.289517 4.745799 4.490378
summary(rock.ppr)
# ..... (same as above)
# .....
#
# Projection direction vectors:
# term 1 term 2
# area1 0.34357179 0.37071027
# peri1 -0.93781471 -0.61923542
# shape 0.04961846 0.69218595
#
# Coefficients of ridge terms:
# term 1 term 2
# 1.6079271 0.5460971