Getting error using SVM with SURF - c++

Question

Below is my code , which is running fine but after a long processing it show me the run time error
// Initialize constant values
const int nb_cars = files.size();
const int not_cars = files_no.size();
const int num_img = nb_cars + not_cars; // Get the number of images
// Initialize your training set.
cv::Mat training_mat(num_img,dictionarySize,CV_32FC1);
cv::Mat labels(0,1,CV_32FC1);
std::vector<string> all_names;
all_names.assign(files.begin(),files.end());
all_names.insert(all_names.end(), files_no.begin(), files_no.end());
// Load image and add them to the training set
int count = 0;
vector<string>::const_iterator i;
string Dir;
for (i = all_names.begin(); i != all_names.end(); ++i)
{
Dir=( (count < files.size() ) ? YourImagesDirectory : YourImagesDirectory_2);
Mat row_img = cv::imread( Dir +*i, 0 );
detector.detect( row_img, keypoints);
RetainBestKeypoints(keypoints, 20); // retain top 10 key points
extractor->compute( row_img, keypoints, descriptors_1);
//uncluster.push_back(descriptors_1);
descriptors.reshape(1,1);
bow.add(descriptors_1);
++count;
}
int count_2=0;
vector<string>::const_iterator k;
Mat vocabulary = bow.cluster();
dextract.setVocabulary(vocabulary);
for (k = all_names.begin(); k != all_names.end(); ++k)
{
Dir=( (count_2 < files.size() ) ? YourImagesDirectory : YourImagesDirectory_2);
row_img = cv::imread( Dir +*k, 0 );
detector.detect( row_img, keypoints);
RetainBestKeypoints(keypoints, 20);
dextract.compute( row_img, keypoints, descriptors_1);
descriptors_1.reshape(1,1);
training_mat.push_back(descriptors_1);
labels.at< float >(count_2, 0) = (count_2<nb_cars)?1:-1;
++count_2;
}
Error :
OpenCv Error : Formats of input argument do not match() in unknown function , file ..\..\..\src\opencv\modules\core\src\matrix.cpp, line 652
I made the descriptor_1 in second loop to reshape into row for SVM , but error is not solving

Answer 1

I think you are trying to cluster with less features then the number of classes.
You can take more images or more then 10 descriptors from each image.

Answer 2

As far i find out after 3 days that my error is in labeling , when i label the image i got the error there , and yes above answer is also relevant that using less number of images also cause the error , but in my case this is not the reason , When i start checking error line by line , the error starts from here :
labels.at< float >(count_2, 0) = (count_2<nb_cars)?1:-1;
Because of the line :
Mat labels(0,1,CV_32FC1);
Instead of :
Mat labels(num_img,1,CV_32FC1);
and i should use
my_img.convertTo( training_mat.row(count_2), CV_32FC1 );