fix: make col_sample min equals to 1 (#385)

Co-authored-by: Mahmoud <mhegab@raisaenergy.com>

Author: HEGAB7

ngboost/ngboost.py

@@ -35,6 +35,7 @@ class NGBoost:
         n_estimators      : the number of boosting iterations to fit
         learning_rate     : the learning rate
         minibatch_frac    : the percent subsample of rows to use in each boosting iteration
+        col_sample        : the percent subsample of columns to use in each boosting iteration
         verbose           : flag indicating whether output should be printed during fitting
         verbose_eval      : increment (in boosting iterations) at which output should be printed
         tol               : numerical tolerance to be used in optimization
@@ -147,7 +148,10 @@ def sample(self, X, Y, sample_weight, params):
             )
 
         if self.col_sample != 1.0:
-            col_size = int(self.col_sample * X.shape[1])
+            if self.col_sample > 0.0:
+                col_size = max(1, int(self.col_sample * X.shape[1]))
+            else:
+                col_size = 0
             col_idx = self.random_state.choice(
                 np.arange(X.shape[1]), col_size, replace=False
             )