diff --git a/example/gnuplot_ex.cpp b/example/gnuplot_ex.cpp
index 2c429db..99d77e8 100644
--- a/example/gnuplot_ex.cpp
+++ b/example/gnuplot_ex.cpp
@@ -25,6 +25,7 @@
  * Also add information on how to contact you by electronic and paper mail.
  ******************************************************/
 
+#include "../lib/core/macro.h"
 #include "../lib/graphic/gnuplot.h"
 
 int main(int argc, char *argv[])
@@ -32,8 +33,8 @@ int main(int argc, char *argv[])
     gctl::gnuplot gt;
 
     //one line test
-    gt.send("set terminal dumb");
-    gt.send("plot [-pi/2:pi] cos(x),-(sin(x) > sin(x+1) ? sin(x) : sin(x+1))");
+    //gt.send("set terminal dumb");
+    //gt.send("plot [-pi/2:pi] cos(x),-(sin(x) > sin(x+1) ? sin(x) : sin(x+1))");
 
     //buffer test (bessel animation)
     /*
@@ -72,16 +73,25 @@ int main(int argc, char *argv[])
     */
 
     //data test
-    /*
+    std::vector<double> x(101);
+    std::vector<double> y1(101);
+    std::vector<double> y2(101);
+    for (size_t i = 0; i < 101; i++)
+    {
+        x[i] = -1.0*GCTL_Pi + 2.0*GCTL_Pi*i/100.0;
+        y1[i] = sin(x[i]);
+        y2[i] = cos(x[i]);
+    }
+
+    std::vector<std::vector<double> > data;
+    data.push_back(x);
+    data.push_back(y1);
+    data.push_back(y2);
+
     gt.to_buffer();
-    gt.send("$Data << EOD");
-    gt.send("0 0 0");
-    gt.send("1 1 0.5");
-    gt.send("2 4 2");
-    gt.send("3 9 3");
-    gt.send("EOD");
+    gt.send_data("$Data", data);
     gt.send("plot $Data using 1:2 with lines title 'y1', '' using 1:3 with lines title 'y2'");
+    gt.save_buffer("sin_cos");
     gt.send_buffer();
-    */
     return 0;
 }
diff --git a/lib/graphic/gnuplot.cpp b/lib/graphic/gnuplot.cpp
index 0c73243..0e3e750 100644
--- a/lib/graphic/gnuplot.cpp
+++ b/lib/graphic/gnuplot.cpp
@@ -72,6 +72,52 @@ void gctl::gnuplot::send_buffer(size_t repeat)
     return;
 }
 
+void gctl::gnuplot::send_data(std::string name, const std::vector<std::vector<double> > &data, bool next_block)
+{
+    if (!pipe) return;
+
+    if (!_2buffer)
+    {
+        fputs((name + " << EOD\n").c_str(), pipe);
+
+        int cnum = data.size();
+        int dnum = data[0].size();
+        std::string line;
+        for (size_t i = 0; i < dnum; i++)
+        {
+            line = std::to_string(data[0][i]);
+            for (size_t j = 1; j < cnum; j++)
+            {
+                line += " " + std::to_string(data[j][i]); 
+            }
+            fputs((line + "\n").c_str(), pipe);
+        }
+
+        fputs("EOD\n", pipe);
+    }
+    else
+    {
+        buffer.push_back(name + " << EOD\n");
+
+        int cnum = data.size();
+        int dnum = data[0].size();
+        std::string line;
+        for (size_t i = 0; i < dnum; i++)
+        {
+            line = std::to_string(data[0][i]);
+            for (size_t j = 1; j < cnum; j++)
+            {
+                line += " " + std::to_string(data[j][i]); 
+            }
+            buffer.push_back(line + "\n");
+        }
+
+        buffer.push_back("EOD\n");
+        if (next_block) buffer.push_back("\n");
+    }
+    return;
+}
+
 void gctl::gnuplot::save_buffer(const std::string& filename)
 {
     time_t now = time(0);
diff --git a/lib/graphic/gnuplot.h b/lib/graphic/gnuplot.h
index 1093df9..73b9f32 100644
--- a/lib/graphic/gnuplot.h
+++ b/lib/graphic/gnuplot.h
@@ -49,6 +49,7 @@ namespace gctl
          * @param persist Gnuplot will hold the window after plot if true.
          */
         gnuplot(bool persist = true);
+
         // destructor
         virtual ~gnuplot();
 
@@ -65,6 +66,15 @@ namespace gctl
          */
         void send(const std::string& cmd, bool next_block = false);
 
+        /**
+         * @brief Send a data block
+         * 
+         * @param name Name of the data block which could be used later for ploting.
+         * @param data data block. Note that each vector object represents a data column.
+         * @param next_block If true, an empty line will be added to the buffer after the cmd.
+         */
+        void send_data(std::string name, const std::vector<std::vector<double> > &data, bool next_block = false);
+
         /**
          * @brief Send the buffer to gnuplot and execute it at once. Then clear the buffer.
          * 
@@ -85,6 +95,7 @@ namespace gctl
 
         FILE* pipe;
         std::vector<std::string> buffer;
+        std::vector<std::string> data_lines;
         bool _2buffer;
     };
 };