MATLAB Programming Fundamentals - MathWorks

You can make selected elements undefined without removing a category or changing

the categories of other elements. Set elements to be undefined to indicate elements

with values that are unknown.

Preallocate Categorical Arrays with Undefined Elements

You can use undefined elements to preallocate the size of a categorical array for better

performance. Create a categorical array that has elements with known locations only.

definedIndex = ~isundefined(Location);

newLocation = Location(definedIndex);

summary(newLocation)

St. Mary's Medical Center 23

Expand the size of newLocation so that it is a 200-by-1 categorical array. Set the last

new element to be undefined. All of the other new elements also are set to be

undefined. The 23 original elements keep the values they had.

newLocation(200) = '<undefined>';

summary(newLocation)

St. Mary's Medical Center 23

<undefined> 177

newLocation has room for values you plan to store in the array later.

See Also

any | categorical | categories | histogram | isundefined | removecats |

summary

Related Examples

• “Create Categorical Arrays” on page 8-2


• “Convert Text in Table Variables to Categorical” on page 8-7


• “Plot Categorical Data” on page 8-12


• “Compare Categorical Array Elements” on page 8-20


• “Work with Protected Categorical Arrays” on page 8-38

8 Categorical Arrays