helper.py

import numpy as np
import os
import torch



def ensure_dir(file_path):
    '''
    Used to ensure to create the a directory when needed
    :param file_path: path to the file that we want to create
    '''
    directory = os.path.dirname(file_path)
    if not os.path.exists(directory):
        os.makedirs(directory)
    return file_path

def safemean(xs):
    return np.nan if len(xs) == 0 else np.mean(xs)

def explained_variance(ypred, y):
    """
    Computes fraction of variance that ypred explains about y.
    Returns 1 - Var[y-ypred] / Var[y]

    interpretation:
        ev=0  =>  might as well have predicted zero
        ev=1  =>  perfect prediction
        ev<0  =>  worse than just predicting zero

    """
    assert y.ndim == 1 and ypred.ndim == 1
    vary = np.var(y)
    return np.nan if vary==0 else 1 - np.var(y-ypred)/vary

def save_checkpoint(state, path, filename='checkpoint.pth.tar', version=0):
    torch.save(state, ensure_dir(os.path.join(path, version, filename)))