Matlab: Undefined function 'eq' for input arguments of type 'cell'

Question

This code:

if (prefixTree(1,4).prefixTree2(:,2)=='2')
    unique(prefixTree(1,4).prefixTree2(:,3))
end

returns this error:

Undefined function 'eq' for input arguments of type 'cell'.

Why?

Answer 1

The error implies that prefixTree(1,4).prefixTree2(:,2) is a cell array. You can access the individual elements of the second column with prefixTree(1,4).prefixTree2{:,2}. Also, the colon operator implies that there is more than one element in prefixTree(1,4).prefixTree2(:,2) but you're trying to do a scalar comparison. Lastly, you're comparing to a char ('2' as opposed to the number 2) and thus it would be best to use string functions. You can use strcmp to check each element of your cell:

prefixTree(1,4).prefixTree2 = {'1' '2';'3' '2'}; % Example data
strcmp(prefixTree(1,4).prefixTree2(:,2),'2')

Then use any or all to return a scalar for your if statement:

if all(strcmp(prefixTree(1,4).prefixTree2(:,2),'2'))
    ...
end