## 3.7 Summary of R Objects

Throughout last chapter and this one, we have covered all types of R objects including vectors, matrices, arrays, data frames (tibbles), and lists. In this section, we would like to summarize what we have covered and highlight the differences of the different types of objects in terms of their dimensions and the data types they can contain.

Type Section Dim Data Type
Vector 2.1 1 Single
Matrix 3.1 2 Single
Array 3.2 >=3 Single
Data Frame/Tibble 3.3 - 3.4 2 Multiple
List 3.5 1 Multiple

### 3.7.1 Exercises

Suppose there are 3 lions, 5 tigers, 7 birds, and 2 monkeys in the zoo.

1. Write R code to create a named numeric vector zoo1 to represent this information. What’s the storage type of zoo1?
2. If we create a vector zoo2 <- c(3, "lions", "5", "tigers"), what is its storage type? Why?
3. Write R code to create a data frame zoo3 where 3 5 7 2 are in one column and the corresponding animal names are in another column. Then give names to each column according to the class of the corresponding vector (if two columns are of the same type, then you can add different numbers after the variable type, e.g. numeric1, numeric2).
4. Write R code to get the number of birds from zoo3.
5. Write R code to extract rows of zoo3 corresponding to lions and tigers.
6. If the zoo also has 6 pandas, write R code to add a row to zoo3 to represent this information.
7. By now, find out the total number of animals in total are in the zoo? (+ is not permitted)
8. The zoo manager wants to put some parrots to the zoo, but he doesn’t yet know the exact number, how can you add a row to represent this?
9. The zoo manager finds that a tiger ran away, please update the data frame zoo3.
10. Can you use the two columns in zoo3 to create a matrix zoo4? If you can, what type of matrix it will be? How many columns and rows are there in the matrix?
11. Please write R code to create a list zoo5 where the first element is 3 5 7 2, the second element contains the corresponding animal names, and the third element being zoo3. During the creation process, assign names to each element according to its class (choose from vector, matrix, array, data frame, list. If two elements are of the same type, then please add different numbers after the element type, e.g. array1, array2)
12. If the zoo manager wants to extract an element named “array” from zoo5, what will he get?