Distancia entre cidades
1.
matrix.ex = matrix(,4,4)
cidades = ("Atenas", "Madri", "Paris", "Estocolmo")
colnames (matrix.ex) = cidades
rownames (matrix.ex) = cidades
matrix.ex [lower.tri(matrix.ex)]= c(3949, 3000, 3927, 1273, 3188, 1827)
matrix.ex

2.
eurodist

Criando um data frame
1.
cor= c("Claro", "Escuro")
dieta= c("A", "B", "C")
var= c(0.1, 1.1, 3.7, 5.7, -1.2, -1.5, 3.0, -0.4, 0.6, 1.5, -0.1, 2.0, 0.6, -3.0, -0.3, -0.2, 0.3, 1.5)
dataframe = data.frame(rep(cor,each=9), rep(dieta,each=3, times=2), var, check.names=FALSE)
colnames(dataframe)= c("Cor","Dieta","Var")

2.
tapply (dataframe$Var, INDEX=dataframe$Dieta, FUN=mean)
tapply (dataframe$Var, INDEX=dataframe$Cor, FUN=mean)

Criando uma Matrix
1.
matrix.ex3 = matrix(rnorm (15, 10, sd=sqrt(3.6)), ncol=5)
2.
rownames (matrix.ex3) = paste("L",1:3)
colnames (matrix.ex3) = paste("C",1:5)
3.
medias = c(apply(X=matrix.ex3, MARGIN=2, FUN=mean), apply(X=matrix.ex3, MARGIN=1, FUN=mean))
vars = c(apply(X=matrix.ex3, MARGIN=2, FUN=var), apply(X=matrix.ex3, MARGIN=1, FUN=var))
medvar.matrix = data.frame(medias, vars)

Lendo e Salvando seus dados
1.
BIO3 = read.csv ("c:/users/Ricardo/Desktop/R/BIO3.csv", header=T, sep=",")
BIO7 = read.csv ("c:/users/Ricardo/Desktop/R/BIO7.csv", header=T, sep=",")
BIO8 = read.csv ("c:/users/Ricardo/Desktop/R/BIO8.csv", header=T, sep=",")
BIO12 = read.csv ("c:/users/Ricardo/Desktop/R/BIO12.csv", header=T, sep=",")
BIO13 = read.csv ("c:/users/Ricardo/Desktop/R/BIO13.csv", header=T, sep=",")
BIO18 = read.csv ("c:/users/Ricardo/Desktop/R/BIO18.csv", header=T, sep=",")
summary (BIO3)
summary (BIO7)
summary (BIO8)
summary (BIO12)
summary (BIO13)
summary (BIO18)
2.
BIO3.20 = BIO3[BIO3$LAT<(-23),]
BIO3.20 = BIO3.20[,c(1,2,4)]
write.table (BIO3.20, file="c:/users/Ricardo/Desktop/R/BIO320.txt", sep="\t", row.names=FALSE)

Acrescentando Dados de Síntese
1.
biomassa = read.table("biomassaarvores.csv", header=TRUE, sep=",")
2.
summary(biomassa)
3.
biomassa$somfoltro = biomassa$folha+biomassa$tronco
4.
biomassa$arebasa = (pi/4)*(biomassa$dap)^2
5.
talhao.area = tapply(biomassa$arebasa, INDEX=biomassa$talhao, FUN=sum)
6.
talhao.areamean = tapply(biomassa$arebasa, INDEX=biomassa$talhao, FUN=mean)
7.
arvore10cm = biomassa[biomassa$ht>10,]
8.
write.table (arvore10cm, file="c:/users/Ricardo/Desktop/R/arvore10cm.txt", row.names=FALSE, sep="\t")