diff --git a/src/utilities/is/isfreq.m b/src/utilities/is/isfreq.m
index 3bef38a862443c4d29f3480c9bf837a25ef4e8bb..2bb33117bc7c4885d090e3c898f2a23743789f74 100644
--- a/src/utilities/is/isfreq.m
+++ b/src/utilities/is/isfreq.m
@@ -3,12 +3,12 @@ function B = isfreq(A) % --*-- Unitary tests --*--
 % Tests if A can be interpreted as a frequency.
 %
 % INPUTS
-%  o A     scalar integer or character.
+% - A     [integer, char]  scalar, frequency code.
 %
 % OUTPUTS
-%  o B     scalar integer equal to one if A can be interpreted as a frequency, zero otherwise.
+% - B     [logical]        scalar equal to true iff A can be interpreted as a frequency.
 
-% Copyright (C) 2013-2020 Dynare Team
+% Copyright © 2013-2020 Dynare Team
 %
 % This file is part of Dynare.
 %
@@ -28,7 +28,7 @@ function B = isfreq(A) % --*-- Unitary tests --*--
 B = false;
 
 if ischar(A)
-    if isequal(length(A),1) && ismember(upper(A),{'Y','A', 'H', 'Q', 'M', 'W', 'D'})
+    if isequal(length(A),1) && ismember(upper(A),{'Y','A', 'H', 'Q', 'M', 'D'})
         B = true;
         return
     end
@@ -38,108 +38,79 @@ if isnumeric(A) && isequal(length(A),1) && ismember(A,[1 2 4 12 52 365])
     B = true;
 end
 
+return
+
 %@test:1
-%$ try
-%$     boolean = isfreq('w');
-%$     t(1) = true;
-%$ catch
-%$     t(1) = false;
-%$ end
-%$
-%$ if t(1)
-%$     t(2) = dassert(boolean, true);
-%$ end
-%$
-%$ T = all(t);
+try
+    b = isfreq('M') && isfreq(12);
+    t(1) = true;
+catch
+    t(1) = false;
+end
+
+if t(1)
+    t(2) = b;
+end
+
+T = all(t);
 %@eof:1
 
 %@test:2
-%$ try
-%$     boolean = isfreq('W');
-%$     t(1) = true;
-%$ catch
-%$     t(1) = false;
-%$ end
-%$
-%$ if t(1)
-%$     t(2) = dassert(boolean, true);
-%$ end
-%$
-%$ T = all(t);
+try
+    b = isfreq('Q') && isfreq(4);
+    t(1) = true;
+catch
+    t(1) = false;
+end
+
+if t(1)
+    t(2) = b;
+end
+
+T = all(t);
 %@eof:2
 
 %@test:3
-%$ try
-%$     boolean = isfreq('M');
-%$     t(1) = true;
-%$ catch
-%$     t(1) = false;
-%$ end
-%$
-%$ if t(1)
-%$     t(2) = dassert(boolean, true);
-%$ end
-%$
-%$ T = all(t);
+try
+    b = isfreq('Y') && isfreq(1);
+    t(1) = true;
+catch
+    t(1) = false;
+end
+
+if t(1)
+    t(2) = b;
+end
+
+T = all(t);
 %@eof:3
 
 %@test:4
-%$ try
-%$     boolean = isfreq('Q');
-%$     t(1) = true;
-%$ catch
-%$     t(1) = false;
-%$ end
-%$
-%$ if t(1)
-%$     t(2) = dassert(boolean, true);
-%$ end
-%$
-%$ T = all(t);
+try
+    b = isfreq('H') && isfreq(2);
+    t(1) = true;
+catch
+    t(1) = false;
+end
+
+if t(1)
+    t(2) = b;
+end
+
+T = all(t);
 %@eof:4
 
 %@test:5
-%$ try
-%$     boolean = isfreq('Y');
-%$     t(1) = true;
-%$ catch
-%$     t(1) = false;
-%$ end
-%$
-%$ if t(1)
-%$     t(2) = dassert(boolean, true);
-%$ end
-%$
-%$ T = all(t);
-%@eof:5
-
-%@test:6
-%$ try
-%$     boolean = isfreq('H');
-%$     t(1) = true;
-%$ catch
-%$     t(1) = false;
-%$ end
-%$
-%$ if t(1)
-%$     t(2) = dassert(boolean, true);
-%$ end
-%$
-%$ T = all(t);
-%@eof:6
-
-%@test:7
-%$ try
-%$     boolean = isfreq('D');
-%$     t(1) = true;
-%$ catch
-%$     t(1) = false;
-%$ end
-%$
-%$ if t(1)
-%$     t(2) = dassert(boolean, true);
-%$ end
-%$
-%$ T = all(t);
-%@eof:7
+try
+    b = isfreq('D') && isfreq(365);
+    t(1) = true;
+catch
+    t(1) = false;
+end
+
+if t(1)
+    t(2) = b;
+end
 
+T = all(t);
+%@eof:5
\ No newline at end of file