assignment error with Mat OpenCv - c++

Question

I am working with OpenCV and C++ for a project and I found the following problem: after initializing a mat with the following statement
Mat or_mat=Mat(img->height,img->width,CV_32FC1);
check the following value
or_mat.at <float> (i, j) = atan (fy / fx) / 2 +1.5707963;
After completing returning the mat for the output of the function but when I go to read there are many values ​​that do not correspond to the output. Precise in incorrect values ​​for the I-4.31602e +008 is inserted and if I make a cout the value of the expression is correct. What could be the error??
relevant Code:
Mat or_mat=Mat(img->height,img->width,CV_32FC1);
to angle
if(fx > 0){
or_mat.at<float>(i,j) = atan(fy/fx)/2+1.5707963;
}
else if(fx<0 && fy >0){
or_mat.at<float>(i,j) = atan(fy/fx)/2+3.1415926;
}
else if(fx<0 && fy <0){
or_mat.at<float>(i,j) = atan(fy/fx)/2;
}
else if(fy!=0 && fx==0){
or_mat.at<float>(i,j) = 1.5707963;
}
I have to calculate the local orientation of the fingerprint image, the following code I have omitted several statements and calculations that do not have errors.

Answer 1

I would triple check that you are indexing correctly. The following code shows my initialising a matrix full of zeros, and then filling it with some float using at .at operator. It compiles and runs nicely:
int main()
{
int height = 10;
int width = 3;
// Initialise or_mat to with every element set to zero
cv::Mat or_mat = cv::Mat::zeros(height, width, CV_32FC1);
std::cout << "Original or_mat:\n" << or_mat << std::endl;
// Loop through and set each element equal to some float
float value = 10.254;
for (int i = 0; i < or_mat.rows; ++i)
{
for (int j = 0; j < or_mat.cols; ++j)
{
or_mat.at<float>(i,j) = value;
}
}
std::cout << "Final or_mat:\n" << or_mat << std::endl;
return 0;
}