prevent erroneous array in ppf with _scalar_if_array_all_equal (#5)

* prevent erroneous array in `ppf` with _scalar_if_array_all_equal

* PR comments

Author: hbmartin

betapert/funcs.py

@@ -83,12 +83,18 @@ def log_cdf_eq(x_normalized):
 }
 
 
+def _scalar_if_array_all_equal(array: np.ndarray | float) -> np.float64 | np.ndarray | float:
+    if isinstance(array, np.ndarray) and array.size != 0 and np.all(array == array[0]):
+        return array[0]
+    return array
+
+
 def _calc_alpha_beta(
     mini: np.float64 | np.ndarray | float,
     mode: np.float64 | np.ndarray | float,
     maxi: np.float64 | np.ndarray | float,
     lambd: np.float64 | np.ndarray | float,
-) -> tuple[np.float64 | np.ndarray | float | int, np.float64 | np.ndarray | float | int]:
+) -> tuple[np.float64 | np.ndarray | float, np.float64 | np.ndarray | float]:
     """Calculate alpha and beta parameters for the underlying beta distribution.
 
     Args:
@@ -107,10 +113,9 @@ def _calc_alpha_beta(
     if DEBUG and any(isinstance(x, np.ndarray) for x in (mini, mode, maxi, lambd)):
         sys.stderr.write("CAB: unexpected arrays in method parameters\n")
     if isinstance(alpha, np.ndarray) and isinstance(beta, np.ndarray):
-        if np.all(alpha == alpha[0]) and np.all(beta == beta[0]):
-            return alpha[0], beta[0]
         if DEBUG:
             sys.stderr.write(f"CAB: Unexpected arrays: alpha={alpha}, beta={beta}\n")
+        return _scalar_if_array_all_equal(alpha), _scalar_if_array_all_equal(beta)
     return alpha, beta
 
 
@@ -130,6 +135,11 @@ def sf(x, mini, mode, maxi, lambd=4):
 
 
 def ppf(q, mini, mode, maxi, lambd=4, *, fallback=None):
+    mini = _scalar_if_array_all_equal(mini)
+    mode = _scalar_if_array_all_equal(mode)
+    maxi = _scalar_if_array_all_equal(maxi)
+    lambd = _scalar_if_array_all_equal(lambd)
+
     alpha, beta = _calc_alpha_beta(mini, mode, maxi, lambd)
     _beta_ppf = mini + (maxi - mini) * scipy.stats.beta.ppf(q, alpha, beta)
     # Use fallback if any values are NaN

pyproject.toml

@@ -1,7 +1,7 @@
 [tool]
 [tool.poetry]
 name = "beta-pert-dist-scipy"
-version = "0.2.0"
+version = "0.2.1"
 homepage = "https://github.com/hbmartin/betapert"
 description = "Top-level package for beta-PERT distribution."
 authors = ["Tom Adamczewski <tadamczewskipublic@gmail.com>", "Harold Martin harold.martin@gmail.com"]