CODEWITHSUNDEEP
pythonpython-3.x
smallvt
smallvt

Reputation: 63

How to carry over variables from past defined functions?

I am writing a program that operates out of a main() function. I am unable to change the main function (this is part of a class). How would I go about carrying over a variable from one function to the next, without changing the main()?

def read_data(fname) :
    file = fname
    x = []
    y = []
    with open(file) as f:
        for line in f:
            xi, yi = [float(x) for x in line.split(",")]
            x.append(xi)
            y.append(yi)
    return x, y   

def compute_m_and_b(x, y) :     
    sx, sy, sx2, sxy, sy2 = 0, 0, 0, 0, 0
    for i in range(len(x)):
        sx += x[i]
        sy += y[i]
        sx2 += (x[i] ** 2)
        sy2 += (y[i] ** 2)
        sxy += (x[i] * y[i])       
    m = (sxy * len(x) - sx * sy) / (sx2 * len(x) - sx**2)
    b = (sy - m * sx) / len(x)
    return m, b

def compute_fx_residual(x, y, m, b) :
    fx = []
    for xi in x:
        fx.append(m * xi + b)    
    residual = []
    for i in range(len(y)):
        residual.append(y[i] - fx[i])
    return fx, residual
        
def compute_sum_of_squared_residuals(residual) :
    least_squares_r = 0
    for i in range(len(y)) :
        least_squares_r += (residual[i]) ** 2
    return least_squares_r

def compute_total_sum_of_squares(y) :
    sum_squares = 0
    ymean = sum(y) / len(y)
    for i in range(len(y)) :
        sum_squares += (yi - ymean) ** 2
    return sum_squares

as you can see, I am restricted to only pulling the variables listed in the parentheses of the def functions. This leads to variables calculated in prior functions being undefined. How can I import them without needing to change the main()?

Please let me know if I should be more clear. I can provide more examples, but I wanted to maintain some brevity.

EDIT: here is the main function:

    def main():
        fname = input("Enter Input Filename: ")
    
        x, y = regress.read_data(fname)
        print()
        print("Input File: ", fname)
        print("Data points: ", len(x))
        
        #compute coefficients m and b
        m, b = regress.compute_m_and_b(x, y)
        
        #compute fx and residual
        fx, residual = regress.compute_fx_residual(x, y, m, b)
        
        #compute sum of squared residuals
        least_squares_r = regress.compute_sum_of_squared_residuals(residual)
        
        #compute sum of squares
        sum_squares = regress.compute_total_sum_of_squares(y)
        
        #compute coefficeint of determination
        coeff_of_d = regress.compute_coeff_of_determination(least_squares_r, sum_squares)
        
        regress.print_least_squares(x, y, m, b, fx, residual, least_squares_r, sum_squares, coeff_of_d)
        
        #compute pearson coefficient
        pearson_r = regress.compute_pearson_coefficient(x, y)
    
        regress.print_pearson(pearson_r)
    
    
        return
    
        
    main()

Upvotes: 1

Views: 134

Answers (1)

blueteeth
blueteeth

Reputation: 3555

You haven't provided the main function so it's unclear how you're currently using it.

Looks to me like you can just get the variable for each consecutive function and pass them into the next:

fname = "some/path/to/file.txt"

x, y = read_data(fname)
m, b = compute_m_and_b(x, y, m, b)
fx, residual = compute_fx_residual(x, y, m, b)
least_squares_r = compute_sum_of_squared_residuals(residual)
sum_squares = compute_total_sum_of_squares(y)

Upvotes: 2

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