Namings | Matrices
R Introduction: Part II

## Namings

By this time, we referred to matrix elements by indices. But in the case of large matrices, it will be quite hard to remember and find where precisely necessary elements are.

This issue can be solved by using names on rows/columns. To set names (stored in `names` vector) of rows for matrix `m` use `rownames(m) <- names`. To set names of columns use the same syntax: `colnames(m) <- names`.

Note

Note that the length of vector names must equal the number of rows or columns respectively. For example, you can not assign 3 column names to a matrix with 4 columns.

For example, let's assign some names to the example matrix.

As you can see, there are names on both rows and columns. If you have names on rows and (or) columns, you can refer to a specific element(s) by using names. You can do it the same way as indexing: specify the name/names of row(s)/column(s) to extract. For example, from the matrix above, we can extract the element `4` (`r2` and `c1`) and the first row (`r1`).

Remember the task with a local furniture store? Assume we have 3 months of selling data.

 Month Sofa Armchair Dining table Dining chair Bookshelf March 16 21 30 23 10 April 40 39 13 21 16 May 11 21 36 32 16

This data is stored in the `sellings` variable without row and column names. Your tasks are:

1. Assign `c("March", "April", "May")` to row names of `sellings`.
2. Assign `c("Sofa", "Armchair, "Dining_table", "Dining_chair", "Bookshelf")` to column names (pay attention to underscore `_` characters!).
3. Output matrix `sellings`.

Everything was clear?

Section 1. Chapter 5

Course Content

# R Introduction: Part II

R Introduction: Part II

## Namings

By this time, we referred to matrix elements by indices. But in the case of large matrices, it will be quite hard to remember and find where precisely necessary elements are.

This issue can be solved by using names on rows/columns. To set names (stored in `names` vector) of rows for matrix `m` use `rownames(m) <- names`. To set names of columns use the same syntax: `colnames(m) <- names`.

Note

Note that the length of vector names must equal the number of rows or columns respectively. For example, you can not assign 3 column names to a matrix with 4 columns.

For example, let's assign some names to the example matrix.

As you can see, there are names on both rows and columns. If you have names on rows and (or) columns, you can refer to a specific element(s) by using names. You can do it the same way as indexing: specify the name/names of row(s)/column(s) to extract. For example, from the matrix above, we can extract the element `4` (`r2` and `c1`) and the first row (`r1`).

Remember the task with a local furniture store? Assume we have 3 months of selling data.

 Month Sofa Armchair Dining table Dining chair Bookshelf March 16 21 30 23 10 April 40 39 13 21 16 May 11 21 36 32 16

This data is stored in the `sellings` variable without row and column names. Your tasks are:

1. Assign `c("March", "April", "May")` to row names of `sellings`.
2. Assign `c("Sofa", "Armchair, "Dining_table", "Dining_chair", "Bookshelf")` to column names (pay attention to underscore `_` characters!).
3. Output matrix `sellings`.

Everything was clear?

Section 1. Chapter 5