diff --git a/src/Matrix.h b/src/Matrix.h
index bb5774f..25ac1fb 100644
--- a/src/Matrix.h
+++ b/src/Matrix.h
@@ -171,6 +171,8 @@ namespace Aurora {
 
         // sub
         double& operator[](size_t index);
+        double operator[](size_t index) const;
+
 
 
         /**
diff --git a/test/Function1D_Test.cpp b/test/Function1D_Test.cpp
index b6f8ad8..a14f175 100644
--- a/test/Function1D_Test.cpp
+++ b/test/Function1D_Test.cpp
@@ -531,6 +531,7 @@ TEST_F(Function1D_Test, nanAndFinite){
 
     double* data = new double[9]{infinite,3,n,2,2,1,4,4,7};
     auto matrix = Aurora::Matrix::fromRawData(data, 9,1,1);
+
     auto r = Aurora::isnan(matrix);
     EXPECT_DOUBLE_EQ(r.getData()[0],0);
     EXPECT_DOUBLE_EQ(r.getData()[1],0);
@@ -543,4 +544,15 @@ TEST_F(Function1D_Test, nanAndFinite){
 
     Aurora::nantoval(matrix,1);
     EXPECT_DOUBLE_EQ(matrix.getData()[2],1);
+
+    double* data2 = new double[1]{n};
+    auto matrix2 = Aurora::Matrix::fromRawData(data, 1,1,1);
+    r = Aurora::isnan(matrix2);
+    EXPECT_DOUBLE_EQ(r.getData()[0],1);
+
+    r = Aurora::isfinite(matrix2);
+    EXPECT_DOUBLE_EQ(r.getData()[0],0);
+
+    Aurora::nantoval(matrix2,1);
+    EXPECT_DOUBLE_EQ(matrix.getData()[0],1);
 }