Not getting right results with abs(x) neg, <cstllib>

[Rafael Olarte]

I really appreciate any feed back in order to resolve this challenge.

My goal is to be able to obtain the error value as follows:

Fahrenheit Centigrade Approximation % Err
-45.38 -42.99 -37.69 12.3

Unfortunately, I am unable to get that result of "12.3" using the abs(x) function.

I really do not know how to deal with negative numbers...

As follows, this is the code I have so far.

Thanks so much for any help I can get in order to resolve this small piece of information.

:)

#include <iostream>
#include <iomanip>
#include <cmath>
#include <cstdlib>
 
using namespace std;
 
int main()
 
{
 
const float temp1 = 38;
const float temp2 = -45.38;
const float temp3 = 89.3495;
 
float tempFahrenheit1;
float tempCelsius1;
 
float tempFahrenheit2;
float tempCelsius2;
 
float tempFahrenheit3;
float tempCelsius3;
 
float friendCal1;
float friendCal2;
float friendCal3;
 
 
float x;
float y;
float z;
 
float resultError1;
float resultError2;
float resultError3;
 
 tempFahrenheit1 =temp1 - 32;
 tempCelsius1 = tempFahrenheit1 * 5/9;
 
 tempFahrenheit2 = temp2 - 32;
 tempCelsius2 = tempFahrenheit2 * 5/9;
 
 tempFahrenheit3 = temp3 - 32;
 tempCelsius3 = tempFahrenheit3 * 5/9;
 
 //Friends calculation
 friendCal1 = (temp1/2) - 15;
 friendCal2 = (temp2/2) - 15;
 friendCal3 = (temp3/2) - 15;
 
 //Percentage Error
 x = friendCal1 - tempCelsius1;
 resultError1 = fabs(x)/tempCelsius1 * 1.0;
 
 y = friendCal2 - tempCelsius2;
 resultError2 = fabs(y)/tempCelsius2 * 1.0;
 
 z = friendCal3 - tempCelsius3;
 resultError3 = fabs(z)/tempCelsius3 * 1.0;
 
 
 
 cout <<fixed << showpoint << setprecision(2);
 
 cout << setw(12) << "Fahrenheit" << setw(12) << "Centigrade" << setw(15)
             << "Approximation" << setw(12) << "% err" << endl; 
 
 cout << setw(12) << temp1 
      << setw(12) << tempCelsius1 
      << fixed << setw(15) << setprecision(2) << friendCal1 
      << fixed << setw(15) << setprecision(2) << resultError1 << endl; 
 
 cout << setw(12) << temp2
      << setw(12) << tempCelsius2
      << fixed << setw(15) << setprecision(2) << friendCal2 
             << fixed << setw(15) << setprecision(2) << resultError2 << endl; 
 
 cout << setw(12) << temp3
      << setw(12) << tempCelsius3
      << fixed << setw(15) << setprecision(2) << friendCal3
      << fixed << setw(15) << setprecision(2) << resultError3 << endl; 
 
 return 0;
 
}
 

[horace1]

try putting abs around the whole expression, e.g.

 //Percentage Error
 x = friendCal1 - tempCelsius1;
 resultError1 = fabs(x/tempCelsius1 * 1.0);
 
 y = friendCal2 - tempCelsius2;
 resultError2 = fabs(y/tempCelsius2 * 1.0);
 
 z = friendCal3 - tempCelsius3;
 resultError3 = fabs(z/tempCelsius3 * 1.0);
 

[Rafael Olarte]

Thank you! It worked excellently well. I had to modified the 1.0 for 100. since it was 100%, and everything worked nice, and smooth.

:)