How do I compare numbers using if and or statements in matlab?

There are different ways to do that:

• Test an individual element against one number

  b(1) == 5

• Test an individual element against several numbers, i.e. is the first element either 1 or 2 or 5?

  b(1) == 1 || b(1) == 2 || b(1) == 5

  %# which is equivalent to

  any(b(1) == [1 2 5];

• Test all (or many) elements against one number

  b == 1; %# a vector with t/f for each element

• Test all elements against several numbers

  b == 1 | b == 2 | b == 5 %# note that I can't use the shortcut ||

  %# this is equivalent to

  ismember(b,[1 2 5])

It is very simple. To test equality of numbers you simply use the == operator.

if (b(1) == 5)
    %% first element of b is 5 
    %% now implement code you require

similarly you can test equality for any element in a matrix. To test for multiple values use the logical or operator || in conjunction with == for example

if (b(1) == 5 || b(1) == 2 || b(1) == 1)
    %% first element of b is 1,2 or 5 
    %% now implement code you require