Histogram Formatting - c++

Question

I am writing a program to create a horizontal histogram from an array of type double data. I was able to get the program to display the boundaries of each sub-interval along with the correct number of asterisks. However, the data is not formatted.
Here's the part of the program responsible for the output:
// endpoints == the boundaries of each sub-interval
// frequency == the number of values which occur in a given sub-interval
for (int i = 0; i < count - 1; i++)
{
cout << setprecision(2) << fixed;
cout << endPoints[i] << " to " << endPoints[i + 1] << ": ";
for (int j = frequency[i]; j > 0; j--)
{
cout << "*";
}
cout << " (" << frequency[i] << ")" << endl;
}
Here's what my output looks like:
0.00 to 3.90: *** (3)
3.90 to 7.80: * (1)
7.80 to 11.70: * (1)
11.70 to 15.60: (0)
15.60 to 19.50: ***** (5)
Here's what I would like it to look like:
00.00 to 04.00: *** (3)
04.00 to 08.00: * (1)
08.00 to 12.00: * (1)
12.00 to 16.00: (0)
16.00 to 20.00: ****** (6)
I've looked up C++ syntax and have found things like setw() and setprecision(). I tried to use both to format my histogram but have not been able to make it look like the model. I was hoping someone could tell me if I'm on the right track and, if so, how to implement setw() and/or setprecision() to properly format my histogram.

Answer 1

Assuming that all numbers are in the [0,100) interval, what you want is a chain of manipulators like:
#include <iostream>
#include <iomanip>
int main() {
std::cout
<< std::setfill('0') << std::setw(5)
<< std::setprecision(2) << std::fixed
<< 2.0
<< std::endl;
return 0;
}
Which will output:
02.00
This is for a single value, you can easily adapt it to suit your needs.
You could, for instance, turn this into an operator and use it like:
#include <iostream>
#include <iomanip>
class FixedDouble {
public:
FixedDouble(double v): value(v) {}
const double value;
}
std::ostream & operator<< (std::ostream & stream, const FixedDouble &number) {
stream
<< std::setfill('0') << std::setw(5)
<< std::setprecision(2) << std::fixed
<< number.value
<< std::endl;
return stream;
}
int main() {
//...
for (int i = 0; i < count - 1; i++) {
std::cout
<< FixedDouble(endPoints[i])
<< " to "
<< FixedDouble(endPoints[i + 1])
<< ": ";
}
for (int j = frequency[i]; j > 0; j--) {
std::cout << "*";
}
std::cout << " (" << frequency[i] << ")" << std::endl;
//...
}