Histogram

When to Use Histograms

Histograms can be used to visualize numerical, date, and datetime data.

Using Histograms in the Cohort Browser

In a histogram in the Cohort Browser, each vertical bar represents the count of records in a particular "bin." Each bin groups records that share the same value or very similar values, in a particular field.

The Cohort Browser automatically groups records into bins, based on the distribution of values in the dataset, for the field in question. Values are distributed in a linear fashion, on the x axis.

Below is a sample histogram showing the distribution of values in a field Critical care total days. Note the label under the chart title, indicating the number of records (203) for which values are shown , and the name of the entity ("RNAseq Notes") to which the data relates.

Non-Numeric Data in Histograms

In some cases, a field containing numeric data may also contain some non-numeric values. These values cannot be represented in a histogram. In such cases, you'll see an following informational message below the chart:

Clicking the "non-numeric values" link will display detail on those values, and the number of record in which each appears:

In Cohort Compare mode, histograms can be used to compare the distribution of values in a field that's common to both cohorts. In this scenario, the distributions are overlaid one atop another. Clicking the "ˇ" icon, in the lower right corner of the tile containing the chart, opens a tooltip showing the cohort names and the colors used to represent data in each.

See Comparing Cohorts for more on using Cohort Compare mode.

Preparing Data for Visualization in Histograms

When ingesting data using Data Model Loader, note that the following data types can be visualized in histograms:

• Integer

• Integer Sparse

• Float

• Float Sparse

• Date

• Date Sparse

• Datetime

• Datetime Sparse