min_number argument in sampling func

btk/create_blend_generator.py

@@ -47,6 +47,7 @@ def __init__(
             )
 
         self.max_number = self.sampling_function.max_number
+        self.min_number = self.sampling_function.min_number
 
     def __iter__(self):
         """Returns an iterable which is the object itself."""
@@ -55,7 +56,7 @@ def __iter__(self):
     def __next__(self):
         """Generates a list of blend tables of len batch_size.
 
-        Each blend table has entries numbered between 1 and max_number, corresponding
+        Each blend table has entries numbered between min_number and max_number, corresponding
         to overlapping objects in the blend.
 
         Returns:
@@ -77,6 +78,11 @@ def __next__(self):
                         f"Number of objects per blend must be "
                         f"less than max_number: {len(blend_table)} <= {self.max_number}"
                     )
+                if len(blend_table) < self.min_number:
+                    raise ValueError(
+                        f"Number of objects per blend must be "
+                        f"greater than min_number: {len(blend_table)} >= {self.min_number}"
+                    )
                 blend_tables.append(blend_table)
             return blend_tables
 

btk/sampling_functions.py

@@ -30,14 +30,16 @@ class SamplingFunction(ABC):
     galaxies chosen for the blend.
     """
 
-    def __init__(self, max_number, seed=DEFAULT_SEED):
+    def __init__(self, max_number, min_number=1, seed=DEFAULT_SEED):
         """Initializes the SamplingFunction.
 
         Args:
             max_number (int): maximum number of catalog entries returned from sample.
+            min_number (int): minimum number of catalog entries returned from sample.
             seed (int): Seed to initialize randomness for reproducibility.
         """
         self.max_number = max_number
+        self.min_number = min_number
 
         if isinstance(seed, int):
             self.rng = np.random.default_rng(seed)
@@ -60,17 +62,20 @@ def compatible_catalogs(self):
 class DefaultSampling(SamplingFunction):
     """Default sampling function used for producing blend tables."""
 
-    def __init__(self, max_number=2, stamp_size=24.0, max_shift=None, seed=DEFAULT_SEED):
+    def __init__(
+        self, max_number=2, min_number=1, stamp_size=24.0, max_shift=None, seed=DEFAULT_SEED
+    ):
         """Initializes default sampling function.
 
         Args:
             max_number (int): Defined in parent class
+            min_number (int): Defined in parent class
             stamp_size (float): Size of the desired stamp.
             max_shift (float): Magnitude of maximum value of shift. If None then it
                              is set as one-tenth the stamp size. (in arcseconds)
             seed (int): Seed to initialize randomness for reproducibility.
         """
-        super().__init__(max_number, seed)
+        super().__init__(max_number=max_number, min_number=min_number, seed=seed)
         self.stamp_size = stamp_size
         self.max_shift = max_shift if max_shift else self.stamp_size / 10.0
 
@@ -104,7 +109,7 @@ def __call__(self, table, shifts=None, indexes=None):
         Returns:
             Astropy.table with entries corresponding to one blend.
         """
-        number_of_objects = self.rng.integers(1, self.max_number + 1)
+        number_of_objects = self.rng.integers(self.min_number, self.max_number)
         (q,) = np.where(table["ref_mag"] <= 25.3)
 
         if indexes is None:
@@ -133,17 +138,20 @@ class BasicSampling(SamplingFunction):
     Includes magnitude cut, restriction on the shape, shift randomization.
     """
 
-    def __init__(self, max_number=4, stamp_size=24.0, max_shift=None, seed=DEFAULT_SEED):
+    def __init__(
+        self, max_number=4, min_number=1, stamp_size=24.0, max_shift=None, seed=DEFAULT_SEED
+    ):
         """Initializes the basic sampling function.
 
         Args:
             max_number (int): Defined in parent class
+            min_number (int): Defined in parent class
             stamp_size (float): Size of the desired stamp.
             max_shift (float): Magnitude of maximum value of shift. If None then it
                              is set as one-tenth the stamp size. (in arcseconds)
             seed (int): Seed to initialize randomness for reproducibility.
         """
-        super().__init__(max_number, seed)
+        super().__init__(max_number=max_number, min_number=min_number, seed=seed)
         self.stamp_size = stamp_size
         self.max_shift = max_shift if max_shift else self.stamp_size / 10.0
 
@@ -169,7 +177,7 @@ def __call__(self, table, **kwargs):
         Returns:
             Table with entries corresponding to one blend.
         """
-        number_of_objects = self.rng.integers(0, self.max_number)
+        number_of_objects = self.rng.integers(self.min_number, self.max_number)
         a = np.hypot(table["a_d"], table["a_b"])
         cond = (a <= 2) & (a > 0.2)
         (q_bright,) = np.where(cond & (table["ref_mag"] <= 24))