我正在寻找帮助来创建动态扩展阵列以从.csv文件导入数据。我不想看到文件有多大并在源代码中编辑变量/提示用户，我只想要导入数据然后以各种方式进行操作。首先，我的代码是：
#include <fstream>
#include <sstream>
#include <iostream>
int main()
{
//declare variables and arrays
long rows = 170260;
int cols = 5;
double **rawData = new double*[rows]; //on heap because of size
for(long pi = 0; pi < rows; ++pi) //create an array of pointers
{
rawData[pi] = new double[cols];
}
char buff[200];
double deltaT;
double carDeltaV;
double *carV = new double[rows]; //on heap because of size
//import raw data
std::cout << "Importing filedata.csv...";
std::ifstream rawInput("filedata.csv");
for(long r = 0; r < rows; ++r)
{
rawInput.getline(buff, 200);
std::stringstream ss(buff);
for(int c = 0; c < cols; ++c)
{
ss.getline(buff, 40, ',');
rawData[r][c] = atof(buff);
}
}
std::cout << "Done." << std::endl;
//create speed matrix
carV[0] = 0;
std::cout << std::endl << "Creating speed matrix...";
for (long i = 1; i < rows; ++i)
{
deltaT = rawData[i][0] - rawData[i-1][0];
carDeltaV = rawData[i-1][3] * deltaT;
carV[i] = carDeltaV + carV[i-1];
}
std::cout << "Done." << std::endl;
//write data to csv file
std::cout << std::endl << "Writing data to file...";
std::ofstream outputData;
outputData.open("outputdata.csv");
for(long r = 0; r < rows; ++r)
{
outputData << rawData[r][0] << "," << rawData[r][3]/.00981 << ",";
outputData << carV[r] << std::endl;
}
outputData.close();
std::cout << "Done." << std::endl;
//delete pointers
std::cout << std::endl << "Clearing memory...";
for(long pj = 0; pj < rows; ++pj)
{
delete [] rawData[pj];
}
delete [] rawData;
delete [] carV;
std::cout << "Done." << std::endl;
std::cin.get();
return 0;
}
注意：colums的数量总是为5.行是我未知的。我将导入的示例如下所示：
0.001098633,0.011430004,0.002829004,-0.004371409,0.00162947
0.001220703,0.00606778,0.001273052,0.003497127,0.002359922
0.001342773,0.003104446,-0.000848701,0.012385657,-0.008119254
还有更多内容，但这应该足以理解我想要实现的目标。我对矢量有点了解，但矢量矢量的概念对我来说有点混乱，我试图实现它没有成功。另外，我读到一个双端队列可能就是我想要的东西？我对这些没有任何经验，而且在我看来，对我的应用程序来说可能有些过分，因为我只是向一个方向追加到一组数据。
免责声明：我几乎是C ++的新手，所以如果你认为有任何概念超出我的技能水平，请告诉我，以便我可以阅读。
有什么建议吗？
编辑：根据请求，这是我尝试使用向量的方法。
std::vector<double> rawDataRow;
std::vector< std::vector<double> > rawDataMatrix;
//import raw data loop
std::ifstream rawInput("test.csv");
for(int i = 1; i > 0; ) {
rawInput.getline(buff, 200);
std::stringstream ss(buff);
for(int c = 0; c < cols; ++c) {
ss.getline(buff, 40, ',');
value = atof(buff);
rawDataRow.push_back(value);
std::cout << rawDataRow[0] << std::endl;
}
timeDiff = timeAfter - timeBefore;
timeBefore = timeAfter;
timeAfter = rawDataRow[0];
rawDataMatrix.push_back(rawDataRow);
}
其中＆＃34;我＆＃34;在eof上将被设置为0。
答案 0 :(得分：0)
总结讨论中出现的问题：
你不能有一个数组向量，请参见：Correct way to work with vector of arrays你可以有一个指向数组的指针向量。但是，在这一点上，我不会搞乱所有的内存处理。
最好的方法是使用向量保存代码，除非您应该在循环中放置rawDataRow的定义以在每次迭代时清除其内容。
std::vector< std::vector<double> > rawDataMatrix;
//import raw data loop
std::ifstream rawInput("test.csv");
for(int i = 1; i > 0; ) {
std::vector<double> rawDataRow;
rawInput.getline(buff, 200);
std::stringstream ss(buff);
// do the rest
}
答案 1 :(得分：0)
看来你的生活太过艰难。但是，关键的实现是，始终需要检查之前的输入以某种形式使用它。一旦你这样做，事情很容易就会到位。
为了方便地处理一行的输入，我要定义的第一件事就是这个简单的操纵器会忽略一个逗号：
std::istream& comma(std::istream& in) {
if ((in >> std::ws).peek() == ',') {
in.ignore(); // the happy case: just skip over the comma
}
else if (!in.peek() == std::char_traits<char>::eof()) {
in.setstate(std::ios_base::failbit); // unhappy: not the end and not a comma
}
return in;
}
有了这个，读取线条并将它们分成单元格相当容易：
std::vector<std::vector<double>> result;
for (std::string line; std::getline(in, line); ) {
std::istringstream lin(line);
std::vector<double> row;
for (double d; d >> lin >> comma; ) {
row.push_back(d);
}
if (!lin.eof()) {
in.setstate(std::ios_base::failbit);
}
std::result.push_back(row);
}
if (!in.eof()) {
std::cout << "there was an input error\n";
}
else {
// result contains the result of reading...
}
我还没有对代码进行过测试，我猜测某些地方存在拼写错误，但一般方法应该正常工作......
答案 2 :(得分：0)
首先，您应该将程序分为三个部分：
你的主程序基本上应该是这样的：
int main() {
vector<InputRecord> data = read_from_csv("filedata.csv");
vector<double> speeds = compute_speeds(data);
write_to_csv("result.csv", data, speeds);
return 0;
}
现在您需要定义InputRecord是什么。你说它是5个双打的阵列，但这不是最好的描述。应该更像这样：
struct InputRecord {
double timestamp;
double field2;
double field3;
double location;
double field5;
};
使用此数据结构，您可以编写data[0].timestamp而不是data[0][0]，这意味着您不再需要评论。
这是我为此任务编写的完整代码。它与你的相似，应该是一个好的起点。请注意，此代码根本不进行显式内存管理。
#include <cstdio>
#include <cstdlib>
#include <fstream>
#include <iostream>
#include <string>
#include <vector>
using std::string;
using std::vector;
struct InputRecord {
double timestamp;
double field2;
double field3;
double location;
double field5;
};
vector<InputRecord> read_from_csv(const char *filename) {
std::ifstream in(filename);
vector<InputRecord> data;
if (!in.is_open()) {
throw std::ios_base::failure(string()
+ "cannot open input file \"" + filename + "\".");
}
string line;
while (std::getline(in, line)) {
InputRecord rec;
char end_of_line;
if (std::sscanf(line.c_str(), "%lf,%lf,%lf,%lf,%lf%c",
&rec.timestamp, &rec.field2, &rec.field3,
&rec.location, &rec.field5, &end_of_line) != 5) {
throw std::ios_base::failure(string()
+ "input file \"" + filename + "\" "
+ "contains invalid data: \"" + line + "\"");
}
data.push_back(rec);
}
if (in.bad()) {
throw std::ios_base::failure(string() + "error while reading data");
}
return data;
}
vector<double> calculate_speeds(const vector<InputRecord> &data) {
vector<double> speeds;
speeds.push_back(0.0);
for (std::size_t i = 1; i < data.size(); i++) {
double delta_t = data[i].timestamp - data[i - 1].timestamp;
double delta_s = data[i].location - data[i - 1].location;
speeds.push_back(delta_s / delta_t);
}
return speeds;
}
void write_to_csv(const char *filename, const vector<InputRecord> &data,
const vector<double> &speeds) {
std::ofstream out(filename);
if (!out.is_open()) {
throw std::ios_base::failure(string()
+ "cannot open output file \"" + filename + "\".");
}
for (std::size_t i = 0; i < data.size(); i++) {
out << data[i].timestamp << "," << speeds[i] << "\n";
}
if (out.bad()) {
throw std::ios_base::failure(string() + "error while writing data");
}
}
int main() {
vector<InputRecord> data = read_from_csv("in.csv");
vector<double> speeds = calculate_speeds(data);
write_to_csv("out.csv", data, speeds);
return 0;
}