Once you have your data in Displayr, and have created some tables, the next step is to perform calculations using these tables as inputs. The results will be displayed in *R Outputs*.

## Introducing *R Outputs*

An *R Output *is a type of calculation in Displayr. It has three defining properties:

- It is an
*output*that appears on a page. It can be anything from a textbox or simple calculation through to data science algorithms or visualizations. Five simple examples are shown in the screenshot from Displayr below. - It uses the
*R*programming language to create the output. You can view the programming*R Output*. The code will appear in the Properties tab of the*object inspector*on the right-hand side of the screen, under the heading**R CODE**. - It has a
**Name**. For example, the table at the top-left of the page is named mytable. To see the name, click**GENERAL**in the Properties window.

You can create an *R Output *by clicking **Insert > Analysis > R Output**, typing some code, and pressing **Calculate** . When this button is red it must be pushed to update the calculation.

## Performing calculations using the cells of a table

You will see 233.0 shown in green on the page above. If you click on it in Displayr, you will see that it contains the following code:

output1 = mytable[3, 2] + mytable[3, 3]

In programming logic, the **Name **of the R Output is shown on the left: output1. This output is the sum of mytable[3, 2] and mytable[3, 3].

The **Name** of the table at the top-left of the screen is mytable. In order to refer to something in a calculation you need to know its name. You can work out the name of any table, R Output, or data by clicking on it and then checking under Properties **> GENERAL > Name**.

The cell in the 3rd row and 2nd column of the table contains the number 64. Thus, mytable[3, 2] is 64. Similarly, mytable[3, 3] is 169. mytable[3, 2] + mytable[3, 3] makes 233, as shown.

**Click here for an interactive tutorial on R calculations**

## Calculations using columns and rows of tables

The *R Output *in the bottom-left contains 5 numbers. If you click on it in Displayr you will see that it contains the following code:

output2 = mytable[, 2] + mytable[, 3]

This means that the *R Output *is called output2. It is the sum of the 2nd and 3rd columns of the table. As the table contains 5 rows, the output contains five values, one for each row. Calculations like this, which involve whole rows or columns of data, are known as *vector arithmetic.*

We could also have achieved the same result using the following code:

output2 = rowSums(mytable[, 2:3])

There are two aspects to this shorter code:

- mytable[, 2:3] represents all of the data from columns 2 through to column 3 of the table. If we had typed mytable[, 1:3] we would get all the columns in the table.
- rowSums computes the sum for each row.

We can also do this same type of calculations on rows. For example, mytable[2, ] + mytable[3, ]means that we want to sum rows 2 and 3. It will return 3 elements.

**Click here for an interactive tutorial on R calculations**

## R Outputs with multiple lines of code

Each of our examples so far has illustrated very simple calculations. Often, there is a need for more complex calculations. This is done by writing multiple lines of code. The following lines of code repeat our earlier example of adding columns 2 and 3:

secondColumn = mytable[, 2] thirdColumn = mytable[, 3] output2 = secondColumn + thirdColumn

There are a few key things to appreciate in this example:

- In the
**R CODE**, we are creating three*objects:*secondColumn, thirdColumn, and output2. - The last object that is created becomes the
*R Output.*The other objects, secondColumn and thirdColumn, are created as intermediate steps in the creation of output2. - Only output2 remains after the computation has been completed, and only output2 can be referred to by other
*R Outputs*.

The next blog post in this series, Introduction to Displayr 5: Machine learning and multivariate statistics, discusses more advanced data science features.