How to round elements in a vector to pre-defined intervals

function gradesRounded = roundGrade(grades)
%roundGrade rounds off each element in a vector to the nearest grade in
%the 7-step scale 
% 
%Input  grades: a vector, each element is a number between -3 and 12
%Output gradesRounded: a vector, each element is a number on the 7-step
%scale

% Start empty vector  
gradesRounded = [];

%Rounded grades
for i=1:length(grades)
    if grades(i) < -1.5
        gradesRounded = -3;
    elseif grades(i) >= -1.5 && grades(i) < 1
        gradesRounded = 0;
    elseif grades(i) >= 1 && grades(i) < 3
        gradesRounded(i) = 2;
    elseif grades(i) >= 3 && grades(i) < 5.5
        gradesRounded(i) = 4;
    elseif grades(i) >= 5.5 && grades(i) < 8.5
        gradesRounded(i) = 7;
    elseif grades(i) >= 8.5 && grades(i) < 11
        gradesRounded(i) = 10;
    elseif grades(i) >= 11
        gradesRounded(i) = 12;
    end

end

So far i have this code.. I have to make a function that takes in a vector with numbers between -3 and 12 and as output it should come out with a vector, where all elements are rounded to the nearest number in a scale that goes: 12 10 7 4 2 00 -3

But when i run the code, l only get one value, not a vector.. I know that the commando l can use is interp1, but isn't there a way l can solve this by using loops?

[Adam]

Your first two case just write to a scalar so if any of those gets hit it will overwrite the vector you are creating in the rest of the cases.

Answer 1

[the cyclist]

Putting Adam's response as an answer instead of a comment, and explaining it in a bit more detail:

In the first and second part of the "if" statement, you have this bit of code

gradesRounded = -3;

instead of this bit of code:

gradesRounded(i) = -3;

which means that you are over-writing your entire vector with a single number, instead of writing to each element of the vector.

[Sandie Nhatien Vu]

Thanks! :-D !!