setwd('U:/public_html/588/Class16/')
data <- read.csv("meadowfoam.csv")
plot(data)
attach(data)

lm1 <- lm(FLOWERS ~ TIME + INTENS)    # here, time is numerical variable
 summary(lm1)

fctime <- factor(TIME)
lm2 <- lm(FLOWERS ~ fctime + INTENS)    # here, time is categorical variable
 summary(lm2)

lm3 <- lm(FLOWERS ~ fctime*INTENS)    # "interaction" model
 summary(lm3)


# this will produce a Book plot 


 plot(FLOWERS ~ INTENS, pch = TIME)   # use different characters for different levels of TIME

 chars = c(1,16)
 plot(FLOWERS ~ INTENS, pch = chars[TIME])   # this uses the fact that TIME = 1 or 2
  abline(a=71.3 , b= -0.04047, lty =2)                        # these numbers are from lm2 fit 
  abline(a=71.3 + 12.16 , b= -0.04047, lty =1)                    # this is for TIME = 2 

  plot(lm2$fit, lm2$res)

detach(data)