Re-type ComputeY as a List.

The number of unique elements in different columns in x1 may be
different, which leads to attempting to add vectors of different length
into res. Previously, `push_back` on a DataFrame changed the DataFrame
to a list, which is being addressed in RcppCore/Rcpp#1099. This change,
combined with attempting to add vectors of different lengths, leads to
an error.

src/testxvalid.cpp

@@ -6,33 +6,33 @@ std::string to_string(T value)
 {
   //create an output string stream
   std::ostringstream os ;
-  
+
   //throw the value into the string stream
   os << value ;
-  
+
   //convert the string stream into a string and return
   return os.str() ;
 }
 using namespace Rcpp;
 
 
 //' Compute the subgroup effect sizes
-//' 
+//'
 //' @param x1 the node labels for each study
 //' @param y  the effect size
 //' @param vi the sampling variance
 //' @param tau2 the residual heterogeneity
 //' @keywords internal
 // [[Rcpp::export(".ComputeY")]]
-DataFrame ComputeY(DataFrame x1, NumericVector y,
+List ComputeY(DataFrame x1, NumericVector y,
                 NumericVector vi, NumericVector tau2) {
   int nsplit;
   int i;
   int j;
-  DataFrame res;
+  List res;
   for (nsplit = 0; nsplit < x1.ncol(); nsplit++) {
     IntegerVector Nodes = x1[nsplit];
-    IntegerVector uniNodes = Rcpp::sort_unique(Nodes); 
+    IntegerVector uniNodes = Rcpp::sort_unique(Nodes);
     NumericVector swyNodes;
     for (i = 0; i < uniNodes.length(); i++) {
       // compute the weighted sum for each node
@@ -43,21 +43,21 @@ DataFrame ComputeY(DataFrame x1, NumericVector y,
           sumWY = sumWY + y[j]/(vi[j]+tau2[nsplit]);
           sumW = sumW + 1/(tau2[nsplit]+vi[j]);
         }
-        
+
       }
      swyNodes.push_back(sumWY/sumW, to_string(uniNodes[i]));
-      
+
     }
-    
+
     res.push_back(swyNodes);
   }
-  
+
   return res;
 
 }
 
 //' Predict effect size for the test set
-//' 
+//'
 //' @param x1 the list of subgroup means
 //' @param x2 predicted subgroup membership for the test set
 //' @keywords internal
@@ -77,7 +77,7 @@ NumericMatrix PredY(List x1, IntegerMatrix x2) {
       } else {
         res(j,i) = SubMeans[to_string(x2(j,i))];
       }
-     
+
       //res(j,i) = x2(j,i);
     }
   }
@@ -86,7 +86,7 @@ NumericMatrix PredY(List x1, IntegerMatrix x2) {
 
 
 //' Replace missing values by the overall weighted mean
-//' 
+//'
 //' @param x1 the two-column matrix of the indices of missing values
 //' @param x2 the matrix of predicted y with missing values
 //' @param y  the effect size
@@ -115,7 +115,7 @@ NumericMatrix ReplaceNA(IntegerMatrix x1, NumericMatrix x2,
   x2(x1(j,0)-1, x1(j,1)-1)  = OverallWM[to_string(x1(j,1))];
   }
   return x2;
-  
+
 }