load the iris dataset
data(iris)
Check out the data and make sure we understand its structure.
head(iris)
## Sepal.Length Sepal.Width Petal.Length Petal.Width Species
## 1 5.1 3.5 1.4 0.2 setosa
## 2 4.9 3.0 1.4 0.2 setosa
## 3 4.7 3.2 1.3 0.2 setosa
## 4 4.6 3.1 1.5 0.2 setosa
## 5 5.0 3.6 1.4 0.2 setosa
## 6 5.4 3.9 1.7 0.4 setosa
We want to calculate a value for every row so lets create a vector for those results.
result <- vector()
Now we are ready to use a control structure and iterate through a dataset.
for(i in 1:nrow(iris)){
result[i] <- iris$Petal.Width[i]/iris$Petal.Length[i]
}
lets plot the results:
plot(result)
That is interesting looks like there might be unique different groups. If we look at the last column we see that there are actually 3 species. The species are in grouped species 1 is on rows 1-50 two is 51-100 and the last one is on rows 101-150. Lets draw some lines to separate the species and see if that makes sense.
plot(result)
abline(v=50, col="red")
abline(v=100, col="red")