Besides the others all saying to cast your index to integer like this:
for k = 0.1 : 0.1 : 360
jArray1(int32(k * 10)) = int32(2);
end
I also want to say that it's usually recommended not to use i and j (though you can) as variable names since they also are the imaginary variable. Hence my new names in the corrected code above.
Also, there are some other ways that are more probably efficient and "MATLAB-ish" to do what you did, such as the methods below:
jArray2 = 2 * ones(1, 3600, 'int32');
jArray3(1 : 3600) = int32(2);
