# Linear regression : ValueError: operands could not be broadcast together with shapes (3,) (1338,)

I try to use linear regression for insurance data . But had error on the when try to call a function with features parameter. Here is my code:

def h(x):
global w
return np.sum(np.transpose(w)*x)
raise NotImplementedError()


when try with a simple data it works fine,

w, x = [1,2,3], [2,3,4]
h(x)


the output is : 20

but when try to use the dataset, it errors:

features = dataset.drop(["charges"], axis=1).values
h(features )


it returns error:

ValueError: operands could not be broadcast together with shapes (3,) (1338,)


so the features looks like this:

array([[0.1173913 , 0.        , 0.35698144, 0.        , 1.        ],
[0.1       , 1.        , 0.48331988, 1.        , 0.        ],
[0.27391304, 1.        , 0.46674738, 3.        , 0.        ],
...,
[0.1       , 0.        , 0.5496099 , 0.        , 0.        ],
[0.15217391, 0.        , 0.3117837 , 0.        , 0.        ],
[0.84782609, 0.        , 0.38216303, 0.        , 1.        ]])


The data i used is insurance.csv from kaggle.com

• You'll have to update your weight vector w for the matrix multiplication to work. Mar 14, 2020 at 17:07
• i'm sorry im new to this field, how to do that? Mar 17, 2020 at 9:23

It looks like you're trying to multiply a matrix and a vector point-wise. Such an operation is not defined. I think you should use X.dot(w), where X is a feature $$\bf matrix$$ and w is the wights $$\bf vector$$. np.dot can operate with objects of different nature (like matrices and vectors). So in h I'd write return X.dot(w). Also, I'd call it only with a matrix X (for consistency), even if there's an object it would be $$X \in \mathbb{R}^{1 \times d}$$ in that case. Watch carefully after shapes of the objects which enter functions.