How to use negative numbers in MatLab

I have a command as

grades=[1,2,3,4,5,6,7,8,9;3,4,5,2.5,-1.5,-1.8,-3,8,4;4,3.5,2,6.7,4,8,4,-2,-1] grades=grades' if grades(i,:)<-1.5 gradesFinal(1,i)=-3;

But MatLab does not convert nr. to -3 as it is should. What is wrong?

Answer 1

[Thorsten]

Use

 grades(grades < - 1.5) = -3;