R列标题标记基于第二个数据框中的水平值

With the following sample data,

使用以下示例数据,

Model <- c(1,1,1,1,1,2,2,2,2,4,4,4,4,3,3,3,3,3)
FactorID <- c  ("Factor1",      "Factor2",      "Factor4",      "Factor3",      "Factor5",      "Factor2",      "Factor3",      "Factor4",      "Factor1",      "Factor2",      "Factor3",      "Factor4",      "Factor1",      "Factor3",      "Factor2",      "Factor4",      "Factor5",      "Factor1")

FactorName<- c("SEK", "GBP",  "USD",  "CAD",  "YEN",  "GBP",  "USD",  "CAD",  "EUR",  "CAD",  "EUR",  "USD",  "GBP",  "YEN",  "CAD",  "EUR",  "USD",  "SEK")

a <- data.frame(Model,FactorID,FactorName)

Model <- c(2,1,3,4)
Factor1 <- c(0.054, 0.113,  0.903,  0.720)
Factor2 <- c(0.885, 0.153,  0.708,  0.750)
Factor3 <- c(0.430, 0.989,  0.518,  0.843)
Factor4 <- c(0.533, 0.6328, 0.343,  0.961)
Factor5 <- c("-",     0.055,  0.699,  "-") 

b <- data.frame(Model,Factor1,Factor2,Factor3,Factor4,Factor5)
M