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Last active January 25, 2022 13:56
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Example of outputting CSV from C++, and picking it up with Python (Matplotlib)
#ifndef UTIL_CSV_WRITER
#define UTIL_CSV_WRITER
/* Optional helper class for outputting CSV data. Use like:
CsvWriter csv("out"); // no .csv suffix
// write individual values
csv.write("foo", "bar");
csv.line();
// or write a whole line at once
csv.line("foo", "bar");
*/
#include <fstream>
#include <string>
#include <sstream>
class CsvWriter {
std::ofstream csvFile;
bool newLine = true;
template<typename V>
void writeValue(V &&v) {
std::stringstream strstr;
strstr << v;
std::string str = strstr.str();
bool needsQuote = false;
for (unsigned i = 0; i < str.size(); ++i) {
if (str[i] == ',') {
needsQuote = true;
break;
}
}
if (needsQuote) {
csvFile << "\"";
for (unsigned i = 0; i < str.size(); ++i) {
if (str[i] == '"') {
csvFile << '"';
}
csvFile << str[i];
}
csvFile << "\"";
} else {
csvFile << v;
}
}
void writeValue(const double &v) {
csvFile << v;
}
void writeValue(const float &v) {
csvFile << v;
}
public:
CsvWriter(std::string name) : csvFile(name + ".csv") {}
CsvWriter & write() {
return *this;
}
template<class First, class... Args>
CsvWriter & write(const First &v, Args ...args) {
if (!newLine) csvFile << ",";
newLine = false;
writeValue(v);
return write(args...);
}
template<typename... T>
CsvWriter & line(T... t) {
write(t...);
csvFile << "\n";
newLine = true;
return *this;
}
};
#endif
#include <fstream>
#include "csv-writer.h"
int main() {
{
// Write it by hand
std::ofstream csvFile("out.csv");
for (float x = 0; x < 1; x += 0.001) {
csvFile << x << "," << (x*x) << "\n";
}
}
{
// Or use the CSV helper class
CsvWriter csv("out-helper");
for (float x = 0; x < 1; x += 0.001) {
csv.line(x, x*x);
}
}
}
import numpy
from matplotlib import pyplot
# Load CSV
data = numpy.loadtxt("out.csv", delimiter=",")
# Basic X/Y plot from the two columns
figure, axes = pyplot.subplots()
axes.plot(data[:,0], data[:,1])
pyplot.savefig("out.svg") # or PNG, etc.
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