I'm working with the iris data-set:
        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
I need to find out that row index which has the maximum value of 'Sepal.Length'