The R Project SVN R

### Examples from: "An Introduction to Statistical Modelling"
###         By Annette Dobson
###
### == with some additions ==

## Plant Weight Data (Page 9)
ctl <- c(4.17,5.58,5.18,6.11,4.50,4.61,5.17,4.53,5.33,5.14)
trt <- c(4.81,4.17,4.41,3.59,5.87,3.83,6.03,4.89,4.32,4.69)
group <- gl(2,10, labels=c("Ctl","Trt"))
weight <- c(ctl,trt)
anova(lm(weight~group))
summary(lm(weight~group-1))


## Birth Weight Data (Page 14)
age <- c(40, 38, 40, 35, 36, 37, 41, 40, 37, 38, 40, 38,
     40, 36, 40, 38, 42, 39, 40, 37, 36, 38, 39, 40)
birthw <- c(2968, 2795, 3163, 2925, 2625, 2847, 3292, 3473, 2628, 3176,
        3421, 2975, 3317, 2729, 2935, 2754, 3210, 2817, 3126, 2539,
        2412, 2991, 2875, 3231)
sex <- gl(2,12, labels=c("M","F"))
if(!is.null(dev.list())) {
    plot(age, birthw, col=codes(sex), main="Dobson's Birth Weight Data")
    lines(lowess(age[sex=='F'], birthw[sex=='F']), col=1)
    lines(lowess(age[sex=='M'], birthw[sex=='M']), col=2)
    legend(40, 2700, c("Female", "Male"), col=1:2, pch=1, lty=1)
}

summary(l1 <- lm(birthw ~ sex + age), cor=TRUE)
summary(l0 <- lm(birthw ~ sex + age -1), cor=TRUE)
anova(l1,l0)
summary(li <- lm(birthw ~ sex + sex:age -1), cor=TRUE)
anova(li,l0)

summary(zi <- glm(birthw ~ sex + age, family=gaussian()))
summary(z0 <- glm(birthw ~ sex + age - 1, family=gaussian()))
anova(zi, z0)

summary(z.o4 <- update(z0, subset = -4))
summary(zz <- update(z0, birthw ~ sex+age-1 + sex:age))
anova(z0,zz)

## Poisson Regression Data (Page 42)
x <- c(-1,-1,0,0,0,0,1,1,1)
y <- c(2,3,6,7,8,9,10,12,15)
summary(glm(y~x,family=poisson(link="identity")))


## Calorie Data (Page 45)
calorie <- data.frame(
              carb = c(33,40,37,27,30,43,34,48,30,38,
              50,51,30,36,41,42,46,24,35,37),
              age  = c(33,47,49,35,46,52,62,23,32,42,
              31,61,63,40,50,64,56,61,48,28),
              wgt  = c(100, 92,135,144,140,101, 95,101, 98,105,
              108, 85,130,127,109,107,117,100,118,102),
              prot = c(14,15,18,12,15,15,14,17,15,14,
              17,19,19,20,15,16,18,13,18,14))
summary(lmcal <- lm(carb~age+wgt+prot, data= calorie))


## Extended Plant Data (Page 59)
ctl <-  c(4.17,5.58,5.18,6.11,4.50,4.61,5.17,4.53,5.33,5.14)
trtA <- c(4.81,4.17,4.41,3.59,5.87,3.83,6.03,4.89,4.32,4.69)
trtB <- c(6.31,5.12,5.54,5.50,5.37,5.29,4.92,6.15,5.80,5.26)
group <- gl(3, length(ctl), labels=c("Ctl","A","B"))
weight <- c(ctl,trtA,trtB)
anova(lmwg <- lm(weight~group))
summary(lmwg)
coef(lmwg)
coef(summary(lmwg))#- incl.  std.err,  t- and P- values.


## Fictitious Anova Data (Page 64)
y <- c(6.8,6.6,5.3,6.1,7.5,7.4,7.2,6.5,7.8,9.1,8.8,9.1)
a <- gl(3,4)
b <- gl(2,2, length(a))
anova(z <- lm(y~a*b))


## Achievement Scores (Page 70)
y <- c(6,4,5,3,4,3,6, 8,9,7,9,8,5,7, 6,7,7,7,8,5,7)
x <- c(3,1,3,1,2,1,4, 4,5,5,4,3,1,2, 3,2,2,3,4,1,4)
m <- gl(3,7)
anova(z <- lm(y~x+m))


## Beetle Data (Page 78)
dose <- c(1.6907, 1.7242, 1.7552, 1.7842, 1.8113, 1.8369, 1.861, 1.8839)
x <- c( 6, 13, 18, 28, 52, 53, 61, 60)
n <- c(59, 60, 62, 56, 63, 59, 62, 60)
dead <- cbind(x, n-x)
summary(     glm(dead ~ dose, family=binomial(link=logit)))
summary(     glm(dead ~ dose, family=binomial(link=probit)))
summary(z <- glm(dead ~ dose, family=binomial(link=cloglog)))
anova(z, update(z, dead ~ dose -1))


## Anther Data (Page 84)
## Note that the proportions below are not exactly
## in accord with the sample sizes quoted below.
## In particular, the value 0.555 does not seem sensible.
n <- c(102,  99,   108,  76,   81,   90)
p <- c(0.539,0.525,0.528,0.724,0.617,0.555)
                    # x <- round(n*p)
x <- n*p
y <- cbind(x,n-x)
f <- rep(c(40,150,350),2)
g <- gl(2,3)
summary(glm(y~g*f,family=binomial(link="logit")))
summary(glm(y~g+f,family=binomial(link="logit")))
summary(glm(y~f,  family=binomial(link="logit")))


## Tumour Data (Page 92)
counts <- c(22,2,10,16,54,115,19,33,73,11,17,28)
type <- gl(4,3,12,labels=c("freckle","superficial","nodular","indeterminate"))
site <- gl(3,1,12,labels=c("head/neck","trunk","extremities"))
data.frame(counts,type,site)
summary(z <- glm(counts ~ type + site,family=poisson()))


## Randomized Controlled Trial (Page 93)
counts <- c(18,17,15,20,10,20,25,13,12)
outcome <- gl(3,1, length(counts))
treatment <- gl(3,3)
summary(z <- glm(counts ~ outcome + treatment,family=poisson()))

## Peptic Ulcers and Blood Groups
counts <- c(579,4219,911,4578,246,3775,361,4532,291,5261,396,6598)
group <- gl(2,1,12,labels=c("cases","controls"))
blood <- gl(2,2,12,labels=c("A","O"))
city  <- gl(3,4,12,labels=c("London","Manchester","Newcastle"))
cbind(codes(group),codes(blood),codes(city),counts)

summary(z1 <- glm(counts ~ group*city + group*blood, family=poisson()),corr=FALSE)
summary(z2 <- glm(counts ~ group*city + blood, family=poisson()), corr=FALSE)
anova(z2,z1)