CODEWITHSUNDEEP
javafor-loop
guccimanilla
guccimanilla

Reputation: 33

For-loop yielding partially correct result

So here is my code, I am trying to calculate the area of a wave:

public class coefficient {
public static void main (String[] args) {

    double f[] = {14.0,18.7,9,4.1,6.7,6,6.3,8.4,4,2.9};
    double T = 10;      
    double area = 0;
    int n = 5;

    double w = 2 * Math.PI / T;

    for (int i = 1; i <= n; i++) {

        System.out.println("n = " + i);

            for (int t = 0; t < f.length; t++) {
                System.out.println("T = " + t + " .......... " + f[t] * Math.cos(i*(w * t)));
                area += f[t] * Math.cos(i*(w * t));
            }

        System.out.printf("\nTotal Area: \t\t%.2f\n", area);
        System.out.printf("Calculated area: \t%.2f\n\n", (2/T)*area);

    }

}

}

So my outputs are correct, except for my total and calculated areas, which are RIGHT when i=1, but after that they don't give me the right answer.

Here's the thing though - when I manually input "i":

area += f[t] * Math.cos(1*(w * t)); OR
area += f[t] * Math.cos(2*(w * t));

I get the right areas! So I think there's something wrong with my for-loop, but I'm not sure what...

So when i = 1, my area output = 15.11. That is correct. Now, when i = 2 in my loop, I SHOULD get 10.06 but instead I'm getting 25.17. I get the correct answer when I manually change i, so i isn't being defined in that line. But it is in the line above it.

Upvotes: 0

Views: 69

Answers (1)

Leo Aso
Leo Aso

Reputation: 12463

Maybe it's because you aren't setting area back to 0 after each iteration. Move the declaration of area into the for loop, and see if that workd.

double f[] = {14.0,18.7,9,4.1,6.7,6,6.3,8.4,4,2.9};
double T = 10;
int n = 5;

double w = 2 * Math.PI / T;

for (int i = 1; i <= n; i++) {      
    double area = 0;

    System.out.println("n = " + i);

    for (int t = 0; t < f.length; t++) {
        System.out.println("T = " + t + " .......... " + f[t] * Math.cos(i*(w * t)));
        area += f[t] * Math.cos(i*(w * t));
    }

    System.out.printf("\nTotal Area: \t\t%.2f\n", area);
    System.out.printf("Calculated area: \t%.2f\n\n", (2/T)*area);

}

Upvotes: 2

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