Example R programs and commands
	   8. R commands for 1-Factor ANOVA with some missing data

# All lines preceded by the "#" character are my comments.
# All other left-justified lines are my input.
# All other indented lines are the R program output.
#
# Tabulated data for input to R
# 
#       ORIGINAL FORMAT
# Skateboarding injuries (per 1000 board-hours.)
#
#  Mar   Jun    Sep  
# 9.7    9.2    9.6 
# 9.8    9.7    9.4 
# 9.6    9.8    8.9 
# 9.5    8.5    9.4 
#        8.4    9.5    
#
#
mar <- c(9.7,9.8,9.6,9.5,NA)   # only 4 values
jun <- c(9.2,9.7,9.8,8.5,8.4)
sep <- c(9.6,9.4,8.9,9.4,9.5)
month <- gl(3,5,labels=c("Mar","Jun","Sep"))
injuries <- c(mar,jun,sep)
result<-anova(lm(injuries~month))
result                  # Shows the ANOVA results

   Analysis of Variance Table

   Response: injuries
	     Df  Sum Sq Mean Sq F value Pr(>F)
   month      2 0.62429 0.31214  1.6749 0.2317
   Residuals 11 2.05000 0.18636


# Nonparametric test for equality of densities:

kruskal.test(list(mar,jun,sep))  # Kruskal-Wallis test

	   Kruskal-Wallis rank sum test

   data:  list(mar, jun, sep)
   Kruskal-Wallis chi-squared = 2.9178, df = 2, p-value = 0.2325


# Alternative, ANOVA-like interface for the Kruskal-Wallis test:

kruskal.test(injuries~month)  # Kruskal-Wallis test

        Kruskal-Wallis rank sum test

   data:  injuries by month
   Kruskal-Wallis chi-squared = 2.9178, df = 2, p-value = 0.2325