Question

Objectives:

• Practice using selection structures within a complete C++ program to solve a problem.
• Be able to understand and use linear interpolation in a program.
• Modify/Extend an existing program.

Problem Description: Linear Interpolation

There are two credit levels for this assignment. Completing the “B” level correctly is worth 16/20 points, completing the “A” level is worth 20/20. You are encouraged to get the code for the “B” level working first and then complete the “A” level if you have time/interest. You should include a comment at the top of your source code that indicates what level you are attempting.

Section 3.5 & 3.6 discuss the application of linear interpolation to determining the freezing point of seawater (based on salinity). In this assignment you will solve a more generalized version of the same problem.

Step 1: Ask the user for a temperature value. If the temperature is within the input temperature range, use linear interpolation to determine and display the corresponding salinity. Otherwise, print a suitable error message.

B-Level

Modification 1: Require the user to enter data values for 3 data samples (two interval ranges). A single sample is a salinity measure and its corresponding temperature. Your program should verify that the salinity values of the three samples are in increasing order and that the temperature values of the three

samples are in decreasing order; if not your program should simply print a message that the data are

invalid and then exit.

• If the samples are correctly ordered, your program should then ask the user to enter a salinity value.
• If the salinity value lies within one of the two input intervals, the program should use

linear interpolation to determine the corresponding temperature.

• If the input value is not within either of the input intervals, then the program should print a message so indicating and exit.

Modification 2: Your program should ask the user what temperature scale to use for your input data (Celsius or Fahrenheit); your program should print computed temperatures in both Celsius and Fahrenheit (your program will need to convert between scales).

Two intervals

Two intervals

input

input

Answer 1

Program

Note: Screenshot is provided for indentation of code with input and output.

Modification 1:-

#include<iostream>
using namespace std;
int main()
{
   float sal1,sal2,sal3;//salinity values
   float temp1,temp2,temp3;//temperature value
   cin>>sal1>>temp1;// user first value for salinity measure and corresponding temperature
   cin>>sal2>>temp2;// user second value for salinity measure and corresponding temperature
   cin>>sal3>>temp3;// user third value for salinity measure and corresponding temperature

   /* checking if salinity values are in increasing order or not
   and if corresponding values of temperature are in decreasing order or not*/
   if(((sal1<sal2)&&(sal2<sal3))&&((temp1>temp2)&&(temp2>temp3)))
   {
       float sal,temp;//saline value to check
       cin>>sal;
       //checking if saline value is present in first interval range or second interval range
       if(sal>sal1&&sal<sal2)
       {
           temp = temp1 + ((temp2-temp1)/(sal2-sal1)) * (sal - sal1);
           cout<<temp<<"\n";
       }
       else if(sal>sal2&&sal<sal3)
       {
           temp = temp2 + ((temp3-temp2)/(sal3-sal2)) * (sal - sal2);
           cout<<temp<<"\n";
       }
       else
       {
           cout<<"wrong saline value -- does not lies in the intervals\n";
       }
   }
   else
   {
       cout<<"Data are invalid";
       return;
   }
}

code:-

Input:

Output:-

Modification 2:-

#include<iostream>
using namespace std;
int main()
{
   float sal1, sal2, sal3; //salinity values
   float temp1, temp2, temp3; //temperature value
   cout << "What scale to use for temperature\n For fahrenheit type 1 and For celsius type 2";
   int x;
   cin >> x; //variable for fahrenheit scale or celsius scale
   cin >> sal1 >> temp1; // user first value for salinity measure and corresponding temperature
   cin >> sal2 >> temp2; // user second value for salinity measure and corresponding temperature
   cin >> sal3 >> temp3; // user third value for salinity measure and corresponding temperature

   /* checking if salinity values are in increasing order or not
   and if corresponding values of temperature are in decreasing order or not*/
   if (((sal1 < sal2) && (sal2 < sal3)) && ((temp1 > temp2) && (temp2 > temp3)))
   {
       float sal, temp; //saline value to check
       cin >> sal;
       //checking if saline value is present in first interval range or second interval range
       if (sal > sal1 && sal < sal2)
       {
           temp = temp1 + ((temp2 - temp1) / (sal2 - sal1)) * (sal - sal1);

           if (x == 1)
           {
               cout << "Fahrenheit temperature is " << temp << "\n";
               //converting fahreinheit to celsius
               float c;
               c = (5.0 / 9.0) * (temp - 32);
               cout << "celsius temperature is " << c << "\n";
           }
           else if (x == 2)
           {
               cout << "celsius temperature is " << temp << "\n";
               float f;
               f = (9.0 * temp / 5.0) + 32;
               cout << "Fahrenheit temperature is " << f << "\n";
           }
       }
       else if (sal > sal2 && sal < sal3)
       {
           temp = temp2 + ((temp3 - temp2) / (sal3 - sal2)) * (sal - sal2);
           if (x == 1)
           {
               cout << "Fahrenheit temperature is " << temp << "\n";
               //converting fahreinheit to celsius
               float c;
               c = (5.0 / 9.0) * (temp - 32);
               cout << "celsius temperature is " << c << "\n";
           }
           else if (x == 2)
           {
               cout << "celsius temperature is " << temp << "\n";
               float f;
               f = (9.0 * temp / 5.0) + 32;
               cout << "Fahrenheit temperature is " << f << "\n";
           }

       }
       else
       {
           cout << "wrong saline value -- does not lies in the intervals\n";
       }
   }
   else
   {
       cout << "Data are invalid";
       return 0;
   }
}

Code screenshot

INPUT:-

OUTPUT;-