diff --git a/src/singlecelldata/cell_data/cell_data.rs b/src/singlecelldata/cell_data/cell_data.rs
index 9745d2b..5248e90 100644
--- a/src/singlecelldata/cell_data/cell_data.rs
+++ b/src/singlecelldata/cell_data/cell_data.rs
@@ -137,6 +137,38 @@ impl CellData{
             *mine += count - double_counts;
         }
     }
+
+    /// adds the other values into this object
+    pub fn merge_re_id_genes(&mut self, other: &CellData, other_genes: &Vec::<usize> ) {
+        self.total_umis += other.total_umis;
+        let mut too_much = BTreeMap::<usize, usize>::new();
+
+        for (gene_umi_combo, counts) in &other.genes {
+            // re-id the UMI count touple
+            let re_ided_umi_combo= GeneUmiHash( 
+                other_genes[gene_umi_combo.0],
+                gene_umi_combo.1
+            );
+            match self.genes.entry(re_ided_umi_combo) {
+                std::collections::btree_map::Entry::Occupied(mut entry) => {
+                    *entry.get_mut() += counts;
+                    let counter = too_much.entry(re_ided_umi_combo.0).or_insert(0);
+                    *counter += 1;
+                }
+                std::collections::btree_map::Entry::Vacant(entry) => {
+                    entry.insert(*counts);
+                }
+            }
+        }
+
+        //let other_total_reads = std::mem::take(&mut other.total_reads);
+        for (gene_id, count) in &other.total_reads {
+            let double_counts = too_much.get(&gene_id).unwrap_or(&0);
+            let mine = self.total_reads.entry(*gene_id).or_insert(0);
+            *mine += count - double_counts;
+        }
+    }
+
     /* my old function
     pub fn merge(&mut self, other:&CellData ){
 
diff --git a/src/singlecelldata/indexed_genes.rs b/src/singlecelldata/indexed_genes.rs
index 8652fdd..d64f78a 100644
--- a/src/singlecelldata/indexed_genes.rs
+++ b/src/singlecelldata/indexed_genes.rs
@@ -25,13 +25,25 @@ impl IndexedGenes{
 		Self{
 			names: BTreeMap::new(),
 			ids_to_name: Vec::with_capacity( 80_000 ),
-			offset : match( off ){
+			offset : match off {
 				Some(o) => o,
 				None => 0,
 			},
 		}
 
 	}
+
+
+	/// merges the other list into this list and returns a Vec of new ids for the other data 
+	pub fn merge (&mut self, other: &IndexedGenes) -> Vec<usize>{
+		let mut rec = Vec::<usize>::with_capacity( other.len() );
+		for gene in &other.ids_to_name {
+			rec.push ( self.get_gene_id( gene ) )
+		}
+		rec
+	}
+
+
 	/// Returns the gene ID for the given gene name.
     /// If the gene does not exist, assigns a new ID.
     pub fn get_gene_id(&mut self, gene: &str) -> usize {
@@ -51,11 +63,15 @@ impl IndexedGenes{
         new_id
     }
 
+    pub fn len( &self ) -> usize{
+    	self.names.len()
+    }
+
 	pub fn new ( data: &BTreeMap<String, usize>, offset: usize ) -> Self {
 		let mut ids_to_name = vec![String::new(); data.len() + offset ];
 		let mut names = BTreeMap::new();
 		let mut max_entry = 0_usize;
-		let _ =data.iter().for_each(| (_,val) | if *val > max_entry {max_entry = *val});
+		let _ = data.iter().for_each(| (_,val) | if *val > max_entry {max_entry = *val});
 		println!("I have gotten a max extry of {max_entry} and have a vec with {} available spaces",ids_to_name.len() );
 		if max_entry > (data.len() + offset) {
 			panic!("This is a library error - why is my largest id {max_entry} when it should be {}?!?",  data.len() + offset);
@@ -73,7 +89,7 @@ impl IndexedGenes{
 	}
 
 	/// returns the external id - the ID used in the single_cell_data class.
-	pub fn ids_for_gene_names(&self, names:&Vec<String> ) -> Vec<usize>{
+	pub fn ids_for_gene_names(&self, names:&Vec::<String> ) -> Vec<usize>{
 		let mut ret = Vec::<usize>::with_capacity( names.len() );
 		for name in names{
 			if let Some(id) = self.names.get( name ){
diff --git a/src/singlecelldata/singlecelldata.rs b/src/singlecelldata/singlecelldata.rs
index 40be9d4..2b4b866 100644
--- a/src/singlecelldata/singlecelldata.rs
+++ b/src/singlecelldata/singlecelldata.rs
@@ -159,6 +159,37 @@ impl SingleCellData{
             }
         }
     }
+
+    /// merge two SingleCellData objects - with a different gene list!!
+    pub fn merge_re_id_genes(&mut self, other: SingleCellData, other_ids: &Vec::<usize> ) {
+        if ! other.is_empty() {
+            // Reset all internal measurements
+            self.checked = false;
+            self.passing = 0;
+            self.genes_with_data.clear();
+
+            for other_cell in other.data.iter().flat_map(|map| map.values()) {
+                let index = self.to_key(&other_cell.name); // Extracting the first u8 of the u64 key
+                match self.data[index].entry(other_cell.name) {
+                    std::collections::btree_map::Entry::Occupied(mut entry) => {
+                        // If cell exists, merge with existing cell
+                        //println!( "merge cell {} {}", other_cell.name, other_cell);
+                        let cell = entry.get_mut();
+                        cell.merge_re_id_genes(other_cell, &other_ids);
+                    }
+                    std::collections::btree_map::Entry::Vacant(entry) => {
+                        // If cell doesn't exist, insert new cell
+                        //println!( "steel cell {} {}", other_cell.name, other_cell);
+                        let mut cell = CellData::new( other_cell.name.clone() );
+                        cell.merge_re_id_genes( other_cell, &other_ids );
+                        entry.insert( cell ); // Move ownership
+                    }
+                }
+            }
+
+        }
+    }
+
     /* // my old fucntion:
     pub fn merge( &mut self, other:&SingleCellData ){
         // reset all internal measurements