diff --git a/example/CMakeLists.txt b/example/CMakeLists.txt
index 20af7b7..6b39b6d 100644
--- a/example/CMakeLists.txt
+++ b/example/CMakeLists.txt
@@ -16,6 +16,7 @@ add_example(spmat_ex OFF)
 add_example(eemd_ex OFF)
 add_example(ceemdan_ex OFF)
 add_example(fft_ex OFF)
+add_example(fft2d_ex OFF)
 add_example(fir_filter_ex OFF)
 add_example(fft_filter_ex OFF)
 add_example(windowfunc_ex OFF)
diff --git a/example/fft2d_ex.cpp b/example/fft2d_ex.cpp
new file mode 100644
index 0000000..7ba4d3d
--- /dev/null
+++ b/example/fft2d_ex.cpp
@@ -0,0 +1,145 @@
+/********************************************************
+ *  ██████╗  ██████╗████████╗██╗
+ * ██╔════╝ ██╔════╝╚══██╔══╝██║
+ * ██║  ███╗██║        ██║   ██║
+ * ██║   ██║██║        ██║   ██║
+ * ╚██████╔╝╚██████╗   ██║   ███████╗
+ *  ╚═════╝  ╚═════╝   ╚═╝   ╚══════╝
+ * Geophysical Computational Tools & Library (GCTL)
+ *
+ * Copyright (c) 2023  Yi Zhang (yizhang-geo@zju.edu.cn)
+ *
+ * GCTL is distributed under a dual licensing scheme. You can redistribute 
+ * it and/or modify it under the terms of the GNU Lesser General Public 
+ * License as published by the Free Software Foundation, either version 2 
+ * of the License, or (at your option) any later version. You should have 
+ * received a copy of the GNU Lesser General Public License along with this 
+ * program. If not, see <http://www.gnu.org/licenses/>.
+ * 
+ * If the terms and conditions of the LGPL v.2. would prevent you from using 
+ * the GCTL, please consider the option to obtain a commercial license for a 
+ * fee. These licenses are offered by the GCTL's original author. As a rule, 
+ * licenses are provided "as-is", unlimited in time for a one time fee. Please 
+ * send corresponding requests to: yizhang-geo@zju.edu.cn. Please do not forget 
+ * to include some description of your company and the realm of its activities. 
+ * Also add information on how to contact you by electronic and paper mail.
+ ******************************************************/
+
+#include "../lib/core.h"
+#include "../lib/io.h"
+#include "../lib/algorithm.h"
+
+using namespace gctl;
+
+double module(std::complex<double> a)
+{
+    return sqrt(a.real()*a.real() + a.imag()*a.imag());
+}
+
+double sin_wave(double t, double f, double phi = 0, double A = 1.0)
+{
+    return A*sin(2*GCTL_Pi*f*t + phi);
+}
+
+void average_radian_spec(const array<double> &in_freq, const array<double> &in_power, 
+    const array<double> &out_freq, array<double> &out_power, array<double> &out_std)
+{
+    int in_num = in_freq.size();
+    int out_num = out_freq.size();
+    out_power.resize(out_num, 0);
+    out_std.resize(out_num, 0);
+
+    std::vector<double> bin;
+    _1d_array bin_arr;
+    for (size_t i = 0; i < out_num; i++)
+    {
+        bin.clear();
+        for (size_t j = 0; j < in_num; j++)
+        {
+            if (in_freq[j] > out_freq[i] - 0.5 && in_freq[j] <= out_freq[i] + 0.5)
+            {
+                bin.push_back(in_power[j]);
+            }
+        }
+
+        if (!bin.empty())
+        {
+            bin_arr.import_vector(bin);
+            out_power[i] = bin_arr.mean();
+            out_std[i] = bin_arr.std();
+        }
+    }
+    return;
+}
+
+int main(int argc, char const *argv[]) try
+{
+    double T = 2.0; // 采样时间
+    double dT = 0.01; // 采样间隔
+    double freq = 1.0/dT; // 采样频率
+
+    int M = round(T/dT) + 1, N = round(T/dT) + 1;
+
+    _2d_matrix sig(M, N);
+    _1d_array X(N), Y(M);
+    _1d_array U(N), V(M);
+    X.sequence(-1.0, dT);
+    Y.sequence(-1.0, dT);
+    U.sequence(-1.0*freq, 2.0*freq/(N - 1));
+    V.sequence(-1.0*freq, 2.0*freq/(M - 1));
+
+    double t;
+    double f1 = 40.0;
+    double f2 = 20.0;
+    double f3 = 10.0;
+    for (size_t i = 0; i < M; i++)
+    {
+        for (size_t j = 0; j < N; j++)
+        {
+            t = sqrt(X[j]*X[j] + Y[i]*Y[i]);
+            sig[i][j] = pow(-1, i+j)*(sin_wave(t, f1) + sin_wave(t, f2) + sin_wave(t, f3));
+        }
+    }
+
+    _1cd_array spectrum;
+    dft2d(sig, spectrum);
+
+    _1d_array spec_real(M*N), spec_imag(M*N), spec_power(M*N);
+    for (size_t i = 0; i < M*N; i++)
+    {
+        spec_real[i] = spectrum[i].real();
+        spec_imag[i] = spectrum[i].imag();
+        spec_power[i] = module(spectrum[i]);
+    }
+
+    save_netcdf_grid("fft2d_sig", sig, U, V, "u", "v");
+    append_netcdf_grid("fft2d_sig", spec_real, "u", "v", "real");
+    append_netcdf_grid("fft2d_sig", spec_imag, "u", "v", "imag");
+    append_netcdf_grid("fft2d_sig", spec_power, "u", "v", "power");
+
+    _1d_array pro_freq(M*N), pro_spec(M*N);
+    for (size_t i = 0; i < M; i++)
+    {
+        for (size_t j = 0; j < N; j++)
+        {
+            pro_freq[j + i*N] = sqrt(U[j]*U[j] + V[i]*V[i]);
+            pro_spec[j + i*N] = spec_power[j + i*N];
+        }
+    }
+
+    _1d_array out_freq, out_power, out_std;
+    out_freq.resize(150, 1.0, 1.0);
+    average_radian_spec(pro_freq, pro_spec, out_freq, out_power, out_std);
+
+    std::ofstream ofile;
+    open_outfile(ofile, "fft2d_radian_spec", ".txt");
+    for (size_t i = 0; i < out_freq.size(); i++)
+    {
+        ofile << out_freq[i] << " " <<  out_power[i] << " " << out_std[i] << "\n";
+    }
+    return 0;
+}
+catch(std::exception &e)
+{
+    GCTL_ShowWhatError(e.what(), GCTL_ERROR_ERROR, 0, 0, 0);
+}
\ No newline at end of file
diff --git a/example/fft_filter_ex.cpp b/example/fft_filter_ex.cpp
index a51f7c5..de892c9 100644
--- a/example/fft_filter_ex.cpp
+++ b/example/fft_filter_ex.cpp
@@ -49,8 +49,9 @@ int main(int argc, char const *argv[]) try
     double f3_demo = 15.0;
 
     // Create input signal
-    gctl::array<double> t, signal(int(10.13*fs));
-    gctl::linespace(0.0, 10.13, int(10.13*fs), t);
+    int snum = int(10.13*fs);
+    gctl::array<double> t(snum), signal(snum);
+    t.sequence(0.0, 10.13/(snum - 1));
 
     for (size_t i = 0; i < t.size(); i++)
     {