Section: Flow Control
if and else statements form a control structure for
conditional execution.  The general syntax involves an if
test, followed by zero or more elseif clauses, and finally
an optional else clause:
  if conditional_expression_1
    statements_1
  elseif conditional_expression_2
    statements_2
  elseif conditional_expresiion_3
    statements_3
  ...
  else
    statements_N
  end
Note that a conditional expression is considered true if the real part of the result of the expression contains any non-zero elements (this strange convention is adopted for compatibility with MATLAB).
if statement
     if_test.m
function c = if_test(a)
  if (a == 1)
     c = 'one';
  elseif (a==2)
     c = 'two';
  elseif (a==3)
     c = 'three';
  else
     c = 'something else';
  end
Some examples of if_test in action:
--> if_test(1) ans = one --> if_test(2) ans = two --> if_test(3) ans = three --> if_test(pi) ans = something else