# How to Create and Modify Histograms in Stata

A histogram is a type of chart that uses rectangular bars to represent frequencies. It’s a helpful way to visualize the distribution of data values.

This tutorial explains how to create and modify histograms in Stata.

## How to Create Histograms in Stata

We’ll use a dataset called auto to illustrate how to create and modify histograms in Stata.

First, load the data by typing the following into the Command box:

use http://www.stata-press.com/data/r13/auto

We can get a quick look at the dataset by typing the following into the Command box:

summarize We can see that there are 12 total variables in the dataset.

### Basic Histogram

We can create a histogram for the variable length by using the hist command:

hist length ### Histogram with Frequencies

By default, Stata displays the density on the y-axis. You can change the y-axis to display the actual frequencies by using the freq command:

hist length, freq ### Histogram with Percentages

You can also change the y-axis to display percentages instead of frequencies by using the percent command:

hist length, percent ### Changing the Number of Bins

When you use the hist function in Stata, it automatically tells you how many “bins” it used. For example, in the previous examples it always used 8 bins: However, we can specify the exact number of bins by using the bin() command. For example, the following code tells Stata to use 16 bins instead of 8:

hist length, percent bin(16) We can also tell Stata to use fewer bins:

hist length, percent bin(4) Notice that the more bins you use, the more granularity you can see in the data.

### Adding a Normal Density to a Histogram

You can add a normal density curve to a histogram by using the normal command:

hist length, normal ## How to Modify Histograms in Stata

We can use several different commands to modify the appearance of the histograms.

We can add a title to the plot using the title() command:

hist length, title(“Distribution of Length”) We can also add a subtitle underneath the title using the subtitle() command:

hist length, title(“Distribution of Length”) subtitle(“n = 74 cars”)  