EDA EXERCISE:
1. Import file "volume" from web page "http://user.mendelu.cz/drapela/Forest_Biometry/Data/" into R Studio.
2. Draw histogram for the variable "d" with densities (probabilities) on y axis
3. Add experimental and normal densities into histogram
4. Redraw histogram with user defined breaks and diameter class width 2 cm
5. Redraw histogram with absolute frequences (including experimental and normal densities)
6. Make QQ plot of "d" for normal distribution.
7. Make boxplot of "d".
8. Make boxplot of "h" and display both histograms ("d" and "h") by two adjacent # (side by side) plots (both boxplots in vertical orientation)