Compare Categorical Array Elements

This example shows how to use relational operations with a categorical array.

Create Categorical Array from Cell Array of Strings

Create a 2-by-4 cell array of strings.

C = {'blue' 'red' 'green' 'blue';...
    'blue' 'green' 'green' 'blue'};

colors = categorical(C)
colors = 

     blue      red        green      blue 
     blue      green      green      blue 

colors is a 2-by-4 categorical array.

List the categories of the categorical array.

categories(colors)
ans = 

    'blue'
    'green'
    'red'

Determine If Elements Are Equal

Use the relational operator, eq (==), to compare the first and second rows of colors.

colors(1,:) == colors(2,:)
ans =

     1     0     1     1

Only the values in the second column differ between the rows.

Compare Entire Array to String

Compare the entire categorical array, colors, to the string 'blue' to find the location of all blue values.

colors == 'blue'
ans =

     1     0     0     1
     1     0     0     1

There are four blue entries in colors, one in each corner of the array.

Convert to an Ordinal Categorical Array

Add a mathematical ordering to the categories in colors. Specify the category order that represents the ordering of color spectrum, red < green < blue.

colors = categorical(colors,{'red','green' 'blue'},'Ordinal',true)
colors = 

     blue      red        green      blue 
     blue      green      green      blue 

The elements in the categorical array remain the same.

List the discrete categories in colors.

categories(colors)
ans = 

    'red'
    'green'
    'blue'

Compare Elements Based on Order

Determine if elements in the first column of colors are greater than the elements in the second column.

colors(:,1) > colors(:,2)
ans =

     1
     1

Both values in the second column, red and green, are greater than the corresponding values in the first column, blue.

Find all the elements in colors that are less than 'blue'.

colors < 'blue'
ans =

     0     1     1     0
     0     1     1     0

The function lt (<) indicates the location of all green and red values with 1.

See Also

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