Invalid operands of types 'int' and 'double(double*, double*, int)' to binary operator

Question

We are doing linear regression for a project in class. I have to write a function. I've tried static casting and other ways of changing this "int n" to a double so it doesn't throw an error? Or am I completely on the wrong train of thought?

Function

void linear_regression(double x[], double y[], int n,
                   double *slope, double *y_int)
{    
    double sum_x, sum_y, sum_x_Squared, sum_Squared_x, product_x_y;
    double m = *slope, b = *y_int;

    sum_x = sum_array(x, n);
    sum_y = sum_array(y, n);

    sum_Squared_x = sum_square_array(x, n);
    sum_x_Squared = sum_array(x, n) * sum_array(x, n);

    product_x_y = sum_product_of_arrays(x, y, n);

    //I'm getting an error on the next statement, about the n
    m = ((sum_x * sum_y) - (n * sum_product_of_arrays)) /
            ((sum_x_Squared) - (n * sum_Squared_x));
    b = ((sum_y - (m * sum_x))/(n));

    return;
}

Error message

Invalid operands of types 'int' and 'double(double*, double*, int)' to
binary operator.

Answer 1

In n * sum_product_of_arrays, sum_product_of_arrays is a function you called to get product_x_y. Did you mean to use product_x_y?