Pie diagrams

Pie diagrams are useful to depict proportions.
There are three common applications:

1. Sum up values for a list of variables and display the total of a variables values as the fraction of the sum of all totals (makes only sense if variables have same scale)
2. Sum up values for one variable over categories
3. Depict relative frequencies for one variable

* Pie diagrams
sysuse census, clear

// Show totals or percentages of each variable
// The variables to be displayed have to make sense when combined to a total!
graph pie poplt5 pop5_17 pop18p
// Add percentage to slices and title
graph pie poplt5 pop5_17 pop18p, plabel(_all percent) title("Population by age group")

// Sum up values for one variable over categories 
graph pie pop, over(region) plabel(_all percent) title ("Share of the population by region")

// Depict relative frequencies for one variable 
graph pie, over(region) plabel(_all sum) title("Distribution of states by region") 
// Highlight specific slices
graph pie, over(region) plabel(_all sum) title("Distribution of states by region") pie(1, explode) pie(2, explode)
			

Exercise

Open the pre-installed dataset voter.dta. The dataset contains US voting results for the candidats Clinton, Bush and Perot by income group.

1. Inspect the dataset to see what each variable records.
2. Create pie diagrams for the lowest and the highest income quintile, indicating the fraction of votes each canditate could win within the income group
3. Modify the graph to include a label with the respective % to each slice
4. Add a title to each graph