diff --git a/tool/dsviewer/dsviewer.cpp b/tool/dsviewer/dsviewer.cpp
index d623767..1bd0917 100644
--- a/tool/dsviewer/dsviewer.cpp
+++ b/tool/dsviewer/dsviewer.cpp
@@ -389,6 +389,28 @@ void statistic(const std::vector<std::string> &cmd_units)
     return;
 }
 
+void set_type(const std::vector<std::string> &cmd_units)
+{
+    // type row|col int|float|string <name>
+    if (cmd_units.size() < 4) throw std::runtime_error("type: insufficient parameters.");
+    if (cmd_units[1] == "row")
+    {
+        if (cmd_units[2] == "int") tc.row_type(Int, cmd_units[3]);
+        else if (cmd_units[2] == "float") tc.row_type(Float, cmd_units[3]);
+        else if (cmd_units[2] == "string") tc.row_type(String, cmd_units[3]);
+        else throw std::runtime_error("type: invalid parameters.");
+    }
+    else if (cmd_units[1] == "col")
+    {
+        if (cmd_units[2] == "int") tc.column_type(Int, cmd_units[3]);
+        else if (cmd_units[2] == "float") tc.column_type(Float, cmd_units[3]);
+        else if (cmd_units[2] == "string") tc.column_type(String, cmd_units[3]);
+        else throw std::runtime_error("type: invalid parameters.");
+    }
+    else throw std::runtime_error("type: invalid parameters.");
+    return;
+}
+
 void set_titles(const std::vector<std::string> &cmd_units)
 {
     // title <row|col> <t1>,<t2>,<t3>,... [<id1>,<id2>,<id3>,...]
diff --git a/tool/dsviewer/dsviewer.h b/tool/dsviewer/dsviewer.h
index 5528529..5354cfa 100644
--- a/tool/dsviewer/dsviewer.h
+++ b/tool/dsviewer/dsviewer.h
@@ -53,12 +53,13 @@ void save_file(const std::vector<std::string> &cmd_units);
 void statistic(const std::vector<std::string> &cmd_units);
 void set_enable(const std::vector<std::string> &cmd_units);
 void set_disable(const std::vector<std::string> &cmd_units);
+void set_type(const std::vector<std::string> &cmd_units);
 void set_titles(const std::vector<std::string> &cmd_units);
 void math_func(const std::vector<std::string> &cmd_units);
 void rand_data(const std::vector<std::string> &cmd_units);
 void filt_data(const std::vector<std::string> &cmd_units);
 
-#define CMD_NUM 14
+#define CMD_NUM 15
 const cmd_pair commands[CMD_NUM] = {
     {"quit", quit, "Quit the program."},
     {"info", info, "Show the table information."},
@@ -69,6 +70,7 @@ const cmd_pair commands[CMD_NUM] = {
     {"stats", statistic, "Calculate statistics of the selected columns."},
     {"enable", set_enable, "Enable column/row outputs by name or index."},
     {"disable", set_disable, "Disable column/row outputs by name or index."},
+    {"type", set_type, "Set column/row data types."},
     {"title", set_titles, "Set row and column titles."},
     {"math", math_func, "Preform mathematic operations of column data."},
     {"random", rand_data, "Generate random column data."},
diff --git a/tool/dsviewer/dsviewer.md b/tool/dsviewer/dsviewer.md
index f76bc81..4f47c5c 100644
--- a/tool/dsviewer/dsviewer.md
+++ b/tool/dsviewer/dsviewer.md
@@ -25,6 +25,9 @@ Enable table outputs. If the input file has no row or column names, use inbuild
 #### disable column|row \<name1\> \<name2\> ...
 Disable table outputs. If the input file has no row or column names, use inbuild names `R<id>` and `C<id>` to select the rows and columns.
 
+#### type row|col int|float|string \<name\>
+Set the data type of a row or column. If the input file has no row or column names, use inbuild names `R<id>` and `C<id>` to select the rows and columns.
+
 #### title row|col \<t1\>,\<t2\>,\<t3\>,... [\<id1\>,\<id2\>,\<id3\>,...]
 Set row and column titles. The titles will be assigned sequentially if no index is specified.