Apartado a)

> diam <- c(8.3, 8.6, 8.8, 10.5, 10.5, 10.8, 11, 11)
> alt <- c(70, 65, 63, 72, 81, 83, 66, 75)
> vol <- c(10.3, 10.3, 10.2, 16.4, 18.8, 19.7, 15.6, 16.3)
> Cerezos <- data.frame(diam, alt, vol)

Apartado b)
> plot(Cerezos$alt, Cerezos$vol)

Apartado c)
> reg_lin <- lm(alt ~ vol, data = Cerezos)
> reg_lin

Apaatado d)
> summary(reg_lin)

Apartado e)
>  cor(Cerezos$alt, Cerezos$vol)
[1] 0.8488805


> cor.test(Cerezos$alt, Cerezos$vol)

        Pearson's product-moment correlation

data:  Cerezos$alt and Cerezos$vol
t = 3.9338, df = 6, p-value = 0.00768
alternative hypothesis: true correlation is not equal to 0
95 percent confidence interval:
 0.3588886 0.9720747
sample estimates:
      cor 
0.8488805 

Apartado f)
> reg_lin_mul <- lm(alt ~ vol + diam)
> reg_lin_mul

Call:
lm(formula = alt ~ vol + diam)

Coefficients:
(Intercept)          vol         diam  
     85.340        3.231       -6.135 

Apartado f)
> diam2 <- diam^2
> reg_cuad <- lm(alt ~ vol + diam2)
> reg_cuad

Call:
lm(formula = alt ~ vol + diam2)

Coefficients:
(Intercept)          vol        diam2  
     55.830        3.158       -0.304