Matlab Logic

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Introduction

If/Then Statements

The basic syntax for if statements in Matlab is:

if (condition1)
  % do some work
elseif (condition2)
  % do different work
 .
 .
 .
else
  % do default work
end
if (condition1)
  % do some work
elseif (condition2)
  % do different work
end
if (condition)
  % do some work
else
  % do default work
end
if (condition)
  % do some work
end


Relational Operators

Operator Description Example
a == b Compares a and b and returns "true" if they are equal. If a and b are arrays, this returns an array that provides the comparison of each entry in a and b
comp = (5 == 3);  % comp is "false", comp=0
a = [1 2; 3 5];
b = [2 4; 3 4];
c = a==b;  % c=[0 0; 1 0]
a ~= b Compares a and b and returns "true" if they are NOT equal. If a and b are arrays, this returns an array that provides the comparison of each entry in a and b
comp = (5 ~= 3);  % comp is "true", comp=1
a = [1 2; 3 5];
b = [2 4; 3 4];
c = a~=b;  % c=[1 1; 0 1]
a > b Returns "true" if a is greater than b. If a and b are arrays, this returns an array that provides the comparison of each entry in a and b
comp = (5 > 3);  % comp is "true", comp=1
a = [1 2; 3 5];
b = [2 4; 3 4];
c = a>b;  % c=[0 0; 0 1]
a < b Returns "true" if a is less than b. If a and b are arrays, this returns an array that provides the comparison of each entry in a and b
comp = (5 < 3);  % comp is "false", comp=0
a = [1 2; 3 5];
b = [2 4; 3 4];
c = a<b;  % c=[1 1; 0 0]
a >= b Returns "true" if a is greater than or equal to b. If a and b are arrays, this returns an array that provides the comparison of each entry in a and b
comp = (5 >= 3);  % comp is "false", comp=0
a = [1 2; 3 5];
b = [2 4; 3 4];
c = a>=b;  % c=[0 0; 1 1]
a <= b Returns "true" if a is less than or equal to b. If a and b are arrays, this returns an array that provides the comparison of each entry in a and b
comp = (5 <= 3);  % comp is "true", comp=1
a = [1 2; 3 5];
b = [2 4; 3 4];
c = a<=b;  % c=[1 1; 1 0]


Logical Operators

Operator Description Example
a & b Returns true if BOTH a AND b are true.
a=5;  b=4; c=6;
d = (a>b) & (c>b);         % true
e = (a>b) & (c<b);         % false
f = (a<b) & (c<b);         % false
g = (a>b) & (c>b) & a+b>c; % true.
a | b Returns true if EITHER a OR b are true.
a=5;  b=4; c=6;
d = (a>b) | (c>b);         % true
e = (a>b) | (c<b);         % true
f = (a<b) | (c<b);         % false
g = (a>b) | (c>b) | a+b>c; % true
h = a>b & b>c | c>a;       % true
~a "NOT" operator. You have already seen this in ~=. Returns true if a is false. Otherwise returns false.
a=5;  b=4; c=6;
d = ~(a>b);         % false
e = ~(a>b);         % false


Switch Statements

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The basic syntax of the switch statement in Matlab is:

  switch ( variable )
  case { case1 case 2 }
    % statements...
  case case3
    % statements...
  otherwise
    % default statements
  end