Examples for a lib_tw's function to convert loss/elem to loss/elem-length is added.

README.md

@@ -75,12 +75,16 @@ loss_from_den=den.loss_pow         # For a file w/ single run
 
 loss_den_from_den=loss_elem2den(s_from_den,loss_from_den,file_name_dt,dtl_dt=5e-6)
 
+# Note len(s_from_den) = len(loss_den_from_den) when writing to a file.
+
 #-- An example for a partran out file
 
 ptrn=PARTRAN(file_name_ptrn)
 
 loss_den_from_ptrn=ptrn.loss_den(file_name_dt,dtl_dt=5e-6)
 
+# Note len(ptrn.s) = len(loss_den_from_ptrn) when writing to a file.
+
 ```
 
 ### Library