Print summary of table, timetable, or categorical array in MATLAB

MATLAB provides various ways to store and organize data such as tables, categorical arrays, arrays, timetables, vectors, etc. MATLAB deals with big data used for machine learning and other mathematical functions which require different organization of data. For small data it is efficient to take a look at the entire data and summarize it but, the same cannot be done when you are working with big data or binary data(.mat files).

For such situations, MATLAB provides the summary function which returns a brief summary of the data structure passed to it. It must be noted here that the summary function works only on three type of MATLAB objects:

1. Table
2. Timetable
3. Categorical Array/Vector

In this article, we shall see how to use the summary function on the above-mentioned MATLAB objects.

Print summary of a table, timetable, or categorical array in MATLAB

The syntax of finding summary in MATLAB for any data that can be represented in a tabular form or categorical array or a datetime frame is given by:

s = summary(<object-name>, <optional-argument>)

Here, the object name could be either a table, timetable, or categorical array and the optional argument takes the dimension along which you need a summary. The dimension argument is optional and without it, summary returns the summary along all dimensions.

Summary of a Table

Summary function does not take any optional argument for tables or timetables therefore, we always get the summary of entire tables. Let us see the same with the help of examples.

First, we will create a table from random vectors and then will print out its summary using the summary() function.

Output:

>> rec

rec =

 5x3 table

 emp_id emp_names salaries
 ______ _________ ________

 12 {'Harry'} 1500 
 34 {'Sean' } 5400 
 37 {'Mark' } 2300 
 45 {'Maria'} 3000 
 65 {'Mia' } 9000 

We have created three column vectors above and using them, we created a table named rec. This table would look like this.

Now, we will print the summary of this table by typing the following command in the command space.

Output:

>> summary(rec)

Variables:

 emp_id: 5x1 double

 Values:

 Min 12 
 Median 37 
 Max 65 

 emp_names: 5x1 cell array of character vectors

 salaries: 5x1 double

 Values:

 Min 1500 
 Median 3000 
 Max 9000 

Here, we can see that for the columns that contain numeric data, summary returns statistical values such as minimum, median, and maximum value whereas for the column that contains only text/character data, it simply return the size of the vector.

Summary of Time Tables

Summary function works in the same manner on time tables, as it works on ordinary tables. We pass the timetable object as an input and receive the summary.

In this example, we shall first create a timetable and then shall call the summary function on it.

Output:

>> weather

weather =

 3x1 timetable

 dates temp
 ___________ ____

 20-Apr-2023 20 
 21-Apr-2023 23 
 22-Apr-2023 17 

Here, we have collected a data of temperatures on three dates. Then we created a timetable named weather. Now, we shall call the summary command in the command window to receive the summary of this timetable.

Output:

>> summary(weather)

RowTimes:

 dates: 3x1 datetime
 Values:
 Min 20-Apr-2023 
 Median 21-Apr-2023 
 Max 22-Apr-2023 
 TimeStep 24:00:00 

Variables:

 temp: 3x1 double

 Values:

 Min 17 
 Median 20 
 Max 23 

Here we get similar output as of an ordinary table. Since the first column contains datetime data, we get the minimum, maximum and the median value along with a timestamp. For the second column, we receive summary containing the maximum, minimum and median value of the temperatures.

Summary of Categorical Arrays

We can get the summary of categorical array by simply passing it to the summary command. Here, we get two scenarios. First, when the array is a 1D vector and second when it is a 2D array. We shall see the same with the help of examples.

1D Categorical Arrays

When we call the summary function on a categorical array, it returns the category count of that array. See the following example.

Output:

>> summary(cat)
 bike bus car red ship 
 1 2 1 2 1 

Firstly, we have created a categorical array and then, we called the summary function on it. The output will give us the category count along with the names of the categories.

2D Categorical Arrays

When we call the summary function on a 2D categorical array, it returns the category count along a particular dimension. The default dimension value is 1 i.e., column-wise. Let's see how this work.

Output:

>> summary(cat)
 bike 1 0 
 bus 0 2 
 car 0 1 
 red 2 0 
 ship 1 1

Here, we have created a 2D categorical array with 5 categories. When we call the summary function on this array, it will display the column-wise category count, which is the default option.

Now, we can also retrieve the summary row-wise or along dimension 2. For doing so, we only need to pass the dimension value as 2. See the following code:

Output:

>> summary(cat,2)
 bike bus car red ship 
 0 1 0 1 0 
 0 1 0 0 1 
 1 0 1 0 0 
 0 0 0 1 1 

This code will print the summary (in this case the category count) row-wise. We can clearly verify that all the category counts are given row-wise.

Conclusion

In this article, we explained how to print summary of a table, timetable, or categorical array/vector in MATLAB using the summary function. We explained summary of each object with the help of examples and also described various options available with the summary function.