MATLAB Examples

# Summary Statistics Grouped by Category

This example shows how to compute summary statistics grouped by levels of a categorical variable. You can compute group summary statistics for a numeric array or a dataset array using grpstats.

## Contents

```load hospital ```

The dataset array, hospital, has 7 variables (columns) and 100 observations (rows).

## Compute summary statistics by category.

The variable Sex is a nominal array with two levels, Male and Female. Compute the minimum and maximum weights for each gender.

```stats = grpstats(hospital,'Sex',{'min','max'},'DataVars','Weight') ```
```stats = Sex GroupCount min_Weight max_Weight Female Female 53 111 147 Male Male 47 158 202 ```

The dataset array, stats, has observations corresponding to the levels of the variable Sex. The variable min_Weight contains the minimum weight for each group, and the variable max_Weight contains the maximum weight for each group.

## Compute summary statistics by multiple categories.

The variable Smoker is a logical array with value 1 for smokers and value 0 for nonsmokers. Compute the minimum and maximum weights for each gender and smoking combination.

```stats = grpstats(hospital,{'Sex','Smoker'},{'min','max'},... 'DataVars','Weight') ```
```stats = Sex Smoker GroupCount min_Weight max_Weight Female_0 Female false 40 111 147 Female_1 Female true 13 115 146 Male_0 Male false 26 158 194 Male_1 Male true 21 164 202 ```

The dataset array, stats, has an observation row for each combination of levels of Sex and Smoker in the original data.