Trouble making a matrix out of accessed data

I have a 1x80 structure with a field called 'Task'.

The 'Task' field can either be a or b.

I want to construct a TaskType matrix that is 1x80, that basically says

if Task=='a', then make the corresponding matrix value 1.
if Task=='b', then make the corresponding matrix value 2.
if neither, then make the matrix value 3.

Here's my code so far:

for x=1:length(Structure)
    if Structure(x).Task=='a'
        TaskType(x)=1;
    elseif Structure(x).Task=='b'
        TaskType(x)=2;
    else 
        TaskType(x)=3;
    end
end

My code is returning 'matrix dimensions must agree.'

Answer 1

[the cyclist]

This test worked just fine for me:

% Fill in random tasks
elements = {'a','b','c','fudge'};
tasks = elements(randi(length(elements),[1,80]));
Structure = struct('Task',tasks);

% Apply Daniel's algorithm
for x=1:length(Structure)
    if Structure(x).Task=='a'
        TaskType(x)=1;
    elseif Structure(x).Task=='b'
        TaskType(x)=2;
    else 
        TaskType(x)=3;
    end
end