library(rio)
library(pls)

y = import("./lactin k04.xlsx", which="y")
x = import("./lactin k04.xlsx", which="x")
p = import("./lactin k04.xlsx", which="unknown")

ejemplo <- plsr(x~y)
**Error in model.frame.default(formula = x ~ y) :
  invalid type (list) for variable 'x'**

problema <- predict(ejemplo,p)