c++保存数据到txt文本

string train_txt = "1.txt";
ofstream myfile(train_txt, ios::app);
for (int i = 0; i < eltwise_fc1->channels; ++i){
cv::Mat featureMap(eltwise_fc1->height, eltwise_fc1->width, CV_32F, eltwise_fc1->list + i * (eltwise_fc1->height*eltwise_fc1->width));
IplImage *src;
src = &IplImage(featureMap);
double ImgPixelVal = cvGetReal2D(src, 0, 0);
//输出像素值
myfile << ImgPixelVal << " ";
}
   myfile << endl;