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Pandas DataFrame | dot method
schedule Aug 12, 2023
Last updated local_offer
Tags Python●Pandas
tocTable of Contents
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Pandas DataFrame.dot(~) method is used to compute matrix-vector and matrix-matrix multiplication.
Parameters
1. arr | array-like or Series or DataFrame
The vector or matrix with which to compute the product.
Return Value
A Series is returned if the return value has only one column, otherwise a DataFrame is returned.
Examples
Consider the following DataFrame:
df = pd.DataFrame({"A":[1,2], "B":[3,4]})df
A B0 1 31 2 4
Performing a matrix-vector multiplication
To perform a matrix-vector multiplication:
df.dot([5,6])
0 231 34dtype: int64
Here, we are performing the following calculation:
$$\begin{pmatrix}
1&3\\
2&4
\end{pmatrix}
\begin{pmatrix}
5\\
6
\end{pmatrix}=
\begin{pmatrix}
23\\
34
\end{pmatrix}$$
The return type is a Series since the result only has one column.
Performing a matrix-matrix multiplication
To perform a matrix-matrix multiplication:
df.dot([[5,6], [7,8]])
0 10 26 301 38 44
Here, we are performing the following calculation:
$$\begin{pmatrix}
1&3\\
2&4
\end{pmatrix}
\begin{pmatrix}
5&6\\
7&8
\end{pmatrix}=
\begin{pmatrix}
26&30\\
38&44
\end{pmatrix}$$
Since the return value has multiple columns, we get a DataFrame instead of a Series.
Published by Isshin Inada
Edited by 0 others
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Official Pandas Documentation
https://pandas.pydata.org/pandas-docs/dev/reference/api/pandas.DataFrame.dot.html
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