diff --git a/src/lib/stat/csv.hpp b/src/lib/stat/csv.hpp
index da84a95e0..bc6ef477b 100644
--- a/src/lib/stat/csv.hpp
+++ b/src/lib/stat/csv.hpp
@@ -51,7 +51,6 @@
 #include "lib/null-value.hpp"
 #include "lib/meta/tuple-helper.hpp"
 #include "lib/format-string.hpp"
-#include "lib/format-util.hpp"
 #include "lib/regex.hpp"
 
 #include <limits>
@@ -170,7 +169,10 @@ namespace stat {
       
       operator string()  const
         {
-          return util::join (*this, "\n");
+          std::ostringstream buffer;
+          for (string const& line : *this)
+            buffer << line << '\n';
+          return buffer.str();
         }
       
       
diff --git a/src/lib/stat/data.hpp b/src/lib/stat/data.hpp
index bcb7407b8..932d67472 100644
--- a/src/lib/stat/data.hpp
+++ b/src/lib/stat/data.hpp
@@ -71,7 +71,13 @@
  ** 
  ** std::vector<int>& counters = daz.n.data;
  ** \endcode
- ** 
+ ** \par Variations
+ ** The standard case is to have a table backed by persistent file storage,
+ ** which can be initially empty. Under some conditions, especially for tests
+ ** - the DataFile can be created without filename
+ ** - it can be created from a CSVData, which is a `std::vector` of CSV-strings
+ ** - it can be [rendered into CSV strings](\ref #renderCSV)
+ ** - a (new) storage file name can be [given later](\ref saveAs)
  ** @see DataCSV_test
  **
  */
@@ -198,6 +204,12 @@ namespace stat{
           loadData();
         }
       
+      DataFile (CSVData const& csv)
+        : filename_{}
+        {
+          appendFrom (csv);
+        }
+      
       
       /* === Data Access === */
       
@@ -222,12 +234,15 @@ namespace stat{
           return rowCnt;
         }
       
-      string
-      dumpCSV()  const
+      CSVData
+      renderCSV()  const
         {
-          string csv;
+          CSVData csv{{}};
+          csv.reserve (size()+1);
+          auto header = generateHeaderSpec();
+          std::swap (csv[0], header);
           for (uint i=0; i < size(); ++i)
-            csv += formatCSVRow(i) + '\n';
+            csv.emplace_back (formatCSVRow(i));
           return csv;
         }
       
@@ -291,6 +306,17 @@ namespace stat{
                       });
         }
       
+      void
+      appendFrom (CSVData const& csv)
+        {
+          if (isnil (csv)) return;
+          verifyHeaderSpec (csv[0]);
+          for (size_t row=1; row<csv.size(); ++row)
+            if (not isnil (csv[row]))
+              appendRowFromCSV (csv[row]);
+        }
+      
+      
       
       /** @param lineLimit number of rows to retain, back from the newest */
       void
@@ -408,14 +434,14 @@ namespace stat{
                     });
         }
       
-      string
-      generateHeaderSpec()
+      CSVLine
+      generateHeaderSpec()  const
         {
-          string csv;
+          CSVLine csv;
           forAllColumns(
                   [&](auto& col)
                     {
-                      appendCsvField (csv, col.header);
+                      csv += col.header;
                     });
           return csv;
         }
@@ -448,7 +474,7 @@ namespace stat{
         }
       
       
-      string
+      CSVLine
       formatCSVRow (size_t rownum)  const
         {
           if (this->empty())
@@ -457,11 +483,11 @@ namespace stat{
             throw error::Logic{_Fmt{"Attempt to access row #%d beyond range [0..%d]."}
                                    % rownum % (size()-1)};
           
-          string csvLine;
+          CSVLine csvLine;
           forAllColumns(
                   [&](auto& col)
                     {
-                      appendCsvField (csvLine, col.data.at(rownum));
+                      csvLine += col.data.at(rownum);
                     });
           return csvLine;
         }
diff --git a/tests/library/gnuplot-gen-test.cpp b/tests/library/gnuplot-gen-test.cpp
index d4dd02b16..6ddacf6fe 100644
--- a/tests/library/gnuplot-gen-test.cpp
+++ b/tests/library/gnuplot-gen-test.cpp
@@ -65,7 +65,7 @@ namespace test{
       
       
       /** @test TODO
-       * @todo WIP 4/24 🔁 define ⟶ implement
+       * @todo WIP 4/24 🔁 define ⟶ ✔ implement
        */
       void
       simpeUsage()
@@ -78,12 +78,13 @@ namespace test{
                                                           ,{4,5}
                                                           ,{5,8}
                                                           ,{6,13}
-                                                          ,{7,21}
+                                                          ,{7,21.55}
                                                          }});
           cout << gnuplot <<endl;
         }
       
       
+      
       /** @test TODO
        * @todo WIP 4/24 🔁 define ⟶ implement
        */
diff --git a/tests/library/stat/data-csv-test.cpp b/tests/library/stat/data-csv-test.cpp
index 51210a8c8..1e192686b 100644
--- a/tests/library/stat/data-csv-test.cpp
+++ b/tests/library/stat/data-csv-test.cpp
@@ -327,9 +327,10 @@ namespace test{
           dat.dupRow();
           dat.id = "last";
           dat.off *= -1;
-          // can dump the contents as CSV
-          CHECK (dat.dumpCSV() ==
-R"("",0,0
+          // can render the contents as CSV
+          CHECK (dat.renderCSV() ==
+R"("ID","Value","Offset"
+"",0,0
 "mid",5.5,1
 "last",5.5,-1
 )"_expect);
@@ -364,8 +365,8 @@ R"("ID","Value","Offset"
           auto appended = (CSVLine{} += 5.5) += Symbol();
           CHECK (appended == "5.5,\"⟂\""_expect);
           
-          CHECK (CSVData({"eeny","meeny","miny","moe"}) == "\"eeny\",\"meeny\",\"miny\",\"moe\""_expect);
-          CHECK (CSVData({"eeny , meeny","miny","moe"}) == "\"eeny , meeny\"\n\"miny\"\n\"moe\""_expect); // you dirty dirty dishrag you
+          CHECK (CSVData({"eeny","meeny","miny","moe"}) == "\"eeny\",\"meeny\",\"miny\",\"moe\"\n"_expect);
+          CHECK (CSVData({"eeny , meeny","miny","moe"}) == "\"eeny , meeny\"\n\"miny\"\n\"moe\"\n"_expect); // you dirty dirty dishrag you
           
           auto csv = CSVData{{"la","la","schland"}
                             ,{{3.2,1l,88}
@@ -381,7 +382,23 @@ R"("la","la","schland"
 "mit","mia","ned"
 ";"
 false
+
 )"_expect);
+          
+          VERIFY_FAIL ("Header mismatch in CSV file", TestTab{csv} );
+          
+          csv = CSVData{{"ID","Value","Offset"}
+                       ,{{"Baby","toe"}
+                        }};
+          VERIFY_FAIL ("unable to parse \"toe\"", TestTab{csv} );
+          
+          csv = CSVData{{"ID","Value","Offset"}
+                       ,{{"Baby",1.6180,23}
+                        ,{"Tiger",10101,-5}
+                        }};
+          TestTab dat{csv};
+          CHECK (dat.val == 1.0101e4);
+          CHECK (dat.renderCSV() == string(csv));
         }
     };
   
diff --git a/wiki/thinkPad.ichthyo.mm b/wiki/thinkPad.ichthyo.mm
index 89e6f9028..efc01e3c6 100644
--- a/wiki/thinkPad.ichthyo.mm
+++ b/wiki/thinkPad.ichthyo.mm
@@ -112157,14 +112157,20 @@ Date:&#160;&#160;&#160;Thu Apr 20 18:53:17 2023 +0200<br/>
 </node>
 </node>
 </node>
-<node BACKGROUND_COLOR="#eef0c5" COLOR="#990000" CREATED="1710516999984" ID="ID_476868581" MODIFIED="1710517031610" TEXT="stat::DataSpan mit Lumiera-Iterator-Framework kompatibel machen">
-<icon BUILTIN="pencil"/>
+<node COLOR="#338800" CREATED="1710516999984" ID="ID_476868581" MODIFIED="1712095672484" TEXT="stat::DataSpan mit Lumiera-Iterator-Framework kompatibel machen">
+<icon BUILTIN="button_ok"/>
 <node CREATED="1710517020971" ID="ID_1049280485" MODIFIED="1710517029789" TEXT="das ist ein Vorgriff auf  C++20">
 <icon BUILTIN="idea"/>
 </node>
 <node COLOR="#338800" CREATED="1711836137562" ID="ID_108223729" MODIFIED="1711836155134" TEXT="schon mal free-functions begin() | end() hinzugef&#xfc;gt">
 <icon BUILTIN="button_ok"/>
 </node>
+<node COLOR="#338800" CREATED="1712095673899" ID="ID_179465663" MODIFIED="1712095687761" TEXT="incl. Erzeugen von Teil-Bereichen">
+<icon BUILTIN="button_ok"/>
+</node>
+<node COLOR="#338800" CREATED="1712095688617" ID="ID_503885767" MODIFIED="1712095695468" TEXT="Test: mit lib::explore()">
+<icon BUILTIN="button_ok"/>
+</node>
 </node>
 <node CREATED="1710351128227" ID="ID_1587957134" MODIFIED="1710351136356" TEXT="Erg&#xe4;nzungen">
 <icon BUILTIN="idea"/>
@@ -112186,8 +112192,8 @@ Date:&#160;&#160;&#160;Thu Apr 20 18:53:17 2023 +0200<br/>
 <node COLOR="#435e98" CREATED="1710351185059" ID="ID_431256200" MODIFIED="1710352477645" STYLE="fork" TEXT="saveAs()-Funktion bereistellen"/>
 </node>
 <node COLOR="#338800" CREATED="1711983612740" ID="ID_902546947" MODIFIED="1712089787472" TEXT="vereinfachte / erweiterte CSV-Notation f&#xfc;r Tests">
-<linktarget COLOR="#2a9fe5" DESTINATION="ID_902546947" ENDARROW="Default" ENDINCLINATION="-1334;77;" ID="Arrow_ID_47054806" SOURCE="ID_1350863024" STARTARROW="None" STARTINCLINATION="-1467;-42;"/>
 <linktarget COLOR="#3483c8" DESTINATION="ID_902546947" ENDARROW="Default" ENDINCLINATION="-1334;77;" ID="Arrow_ID_606537608" SOURCE="ID_1834207024" STARTARROW="None" STARTINCLINATION="1430;149;"/>
+<linktarget COLOR="#2a9fe5" DESTINATION="ID_902546947" ENDARROW="Default" ENDINCLINATION="-1334;77;" ID="Arrow_ID_47054806" SOURCE="ID_1350863024" STARTARROW="None" STARTINCLINATION="-1467;-42;"/>
 <icon BUILTIN="button_ok"/>
 <node COLOR="#338800" CREATED="1711983784796" ID="ID_1350290271" MODIFIED="1712081833591" TEXT="CSVLine : string der Felder anh&#xe4;ngen kann">
 <icon BUILTIN="button_ok"/>
@@ -112203,8 +112209,17 @@ Date:&#160;&#160;&#160;Thu Apr 20 18:53:17 2023 +0200<br/>
 <icon BUILTIN="idea"/>
 </node>
 </node>
-<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1712081944646" ID="ID_685990414" MODIFIED="1712081986841" TEXT="kann aus DataTable gewonnen werden">
-<icon BUILTIN="flag-yellow"/>
+<node COLOR="#338800" CREATED="1712081944646" ID="ID_685990414" MODIFIED="1712095588465" TEXT="kann aus DataFile gewonnen werden">
+<icon BUILTIN="button_ok"/>
+<node CREATED="1712095483749" ID="ID_448300363" MODIFIED="1712095501564" TEXT="erscheint nur m&#xe4;&#xdf;ig sinnvoll...">
+<icon BUILTIN="smiley-neutral"/>
+</node>
+<node COLOR="#435e98" CREATED="1712095518601" ID="ID_1818911968" MODIFIED="1712095586479" TEXT="Umgekehrt: die dump-Funktion von DataFile durch CSVData ersetzen">
+<icon BUILTIN="idea"/>
+</node>
+<node COLOR="#435e98" CREATED="1712095554779" ID="ID_1265654486" MODIFIED="1712095586479" TEXT="...und damit ist es auch ein neuer ctor sinnvoll: DataFile{CSVData}">
+<font ITALIC="true" NAME="SansSerif" SIZE="12"/>
+</node>
 </node>
 </node>
 </node>
@@ -112260,10 +112275,6 @@ Date:&#160;&#160;&#160;Thu Apr 20 18:53:17 2023 +0200<br/>
 </node>
 <node COLOR="#338800" CREATED="1711983648446" ID="ID_1858721218" MODIFIED="1712089737113" TEXT="demonnstrate_CSV_Notation">
 <icon BUILTIN="button_ok"/>
-<node COLOR="#228091" CREATED="1711983651689" ID="ID_1350863024" MODIFIED="1712089777858" TEXT="sollte doch noch etwas die Notation von Testdaten vereinfachen">
-<arrowlink COLOR="#2a9fe5" DESTINATION="ID_902546947" ENDARROW="Default" ENDINCLINATION="-1334;77;" ID="Arrow_ID_47054806" STARTARROW="None" STARTINCLINATION="-1467;-42;"/>
-<icon BUILTIN="yes"/>
-</node>
 </node>
 <node COLOR="#338800" CREATED="1710460938455" ID="ID_757574171" MODIFIED="1710466412661" TEXT="verify_persistentDataFile">
 <icon BUILTIN="button_ok"/>
@@ -114421,9 +114432,16 @@ std::cout &lt;&lt; tmpl.render({&quot;what&quot;, &quot;World&quot;}) &lt;&lt; s
 </node>
 <node COLOR="#338800" CREATED="1711820811033" ID="ID_1587185713" MODIFIED="1711904722630" TEXT="Header + Datentupel&lt;double&gt;">
 <icon BUILTIN="button_ok"/>
+<node COLOR="#435e98" CREATED="1712095887150" HGAP="33" ID="ID_675366089" LINK="#ID_1395935730" MODIFIED="1712095932364" TEXT="Umweg &#xfc;ber CSVData" VSHIFT="8">
+<icon BUILTIN="idea"/>
 </node>
 </node>
 </node>
+<node COLOR="#228091" CREATED="1711983651689" ID="ID_1350863024" MODIFIED="1712089777858" TEXT="sollte doch noch etwas die Notation von Testdaten vereinfachen">
+<arrowlink COLOR="#2a9fe5" DESTINATION="ID_902546947" ENDARROW="Default" ENDINCLINATION="-1334;77;" ID="Arrow_ID_47054806" STARTARROW="None" STARTINCLINATION="-1467;-42;"/>
+<icon BUILTIN="yes"/>
+</node>
+</node>
 <node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1711900330296" ID="ID_1080765414" MODIFIED="1711900374682" TEXT="typischerweise: Familie von Aufruf-Front-ends">
 <icon BUILTIN="flag-yellow"/>
 <node CREATED="1711900349274" ID="ID_1386251374" MODIFIED="1711900360595" TEXT="der eigentliche Aufruf kann mit einem Rec::Mutator erfolgen"/>