# Array of differences to mean: differences
differences=versicolor_petal_length-np.mean(versicolor_petal_length)


# Square the differences: diff_sq
diff_sq=np.square(differences)


# Compute the mean square difference: variance_explicit
variance_explicit=np.mean(diff_sq)


# Compute the variance using NumPy: variance_np
variance_np=np.var(versicolor_petal_length)




# Print the results
print(variance_explicit,variance_np)
 

def pearson_r(x, y):
    """Compute Pearson correlation coefficient between two arrays."""
    # Compute correlation matrix: corr_mat
    corr_mat=np.corrcoef(x,y)

    # Return entry [0,1]
    return corr_mat[0,1]

# Compute Pearson correlation coefficient for I. versicolor: r
r=pearson_r(versicolor_petal_length, versicolor_petal_width)

# Print the result
print(r)