在R中的线性模型中检查共线性时，如何解释别名结果？

Question

Being a new to R and modeling. I was working on linear model and saw NA for my model results. So I checked the attached post by Mark Needham checking Co-Linearity using alias function . However, When I performed my aliasing I got -1 and 1. If any one can help me out with interpreting the results, that will be great help. In other words, Is it Ok to say that shuttle service is highly co-related with outdoor pool, but not with Mini bar and spa ? What does -1 and 1 mean ?

Below is my alias results:

Model :
sub1$Likelihood_Recommend_H ~ sub1$`Mini-Bar_PL` + sub1$`Pool-Outdoor_PL` + 
    sub1$Spa_PL + sub1$`Shuttle Service_PL`

Complete :
                           (Intercept) sub1$`Mini-Bar_PL`Y sub1$`Pool-Outdoor_PL`Y sub1$Spa_PLY
sub1$`Shuttle Service_PL`Y  0          -1                   1                      -1          

Thanks in advance,

Answer 1

alias function finds linearly dependent terms in the linear model. So the way to interpret the numbers output by alias is: Shuttle_service_PL = -1*Mini-bar_PL + 1*Pool-Outdoor_PL + 1*Spa_PL