sWMx = max(iris$Sepal.Width)
sWMin = min(iris$Sepal.Width)
sLMx = max(iris$Sepal.Length)
sLMin = min(iris$Sepal.Length)

setosa <- iris[1:50,]
versicolor <-iris[51:100,]
virginica <-iris[101:150,]

plot(setosa$Petal.Length, setosa$Petal.Width, 
bg=rgb(1-((setosa$Sepal.Width- sWMin)/(sWMx-sWMin)), ((setosa$Sepal.Width-sWMin)/(sWMx-sWMin)), 0.0), 
col=rgb(1-((setosa$Sepal.Width- sWMin)/(sWMx-sWMin)), ((setosa$Sepal.Width-sWMin)/(sWMx-sWMin)), 0.0), 
cex= 2 * ((setosa$Sepal.Length - sLMin) / (sLMx - sLMin)),
pch=22,
xlab="Petal Length", ylab="Petal Width",
xlim=c(min(iris$Petal.Length), max(iris$Petal.Length)),
ylim=c(min(iris$Petal.Width), max(iris$Petal.Width)))

points(versicolor$Petal.Length, versicolor$Petal.Width, 
bg=rgb(1-((versicolor$Sepal.Width- sWMin)/(sWMx-sWMin)), ((versicolor$Sepal.Width-sWMin)/(sWMx-sWMin)), 0.0), 
col=rgb(1-((versicolor$Sepal.Width- sWMin)/(sWMx-sWMin)), ((versicolor$Sepal.Width-sWMin)/(sWMx-sWMin)), 0.0), 
cex= 2 * ((versicolor$Sepal.Length - sLMin) / (sLMx - sLMin)),
pch=21)

points(virginica$Petal.Length, virginica$Petal.Width, 
bg=rgb(1-((virginica$Sepal.Width- sWMin)/(sWMx-sWMin)), ((virginica$Sepal.Width-sWMin)/(sWMx-sWMin)), 0.0), 
col=rgb(1-((virginica$Sepal.Width- sWMin)/(sWMx-sWMin)), ((virginica$Sepal.Width-sWMin)/(sWMx-sWMin)), 0.0), 
cex= 2 * ((virginica$Sepal.Length - sLMin) / (sLMx - sLMin)),
pch=24)