I have 2 dataframes. I would like to broadcast a divide operation
df1= pd.DataFrame([[1.,2.,3.,4.], [5.,6.,7.,8.], [9.,10.,11.,12.]],
columns=['A','B','C','D'], index=['x','y','z'])
df2= pd.DataFrame([[0.,1.,2.,3.]], columns=['A','B','D','C'], index=['q'])
Notice that the columns are aligned slightly differently in df2.
I would like to divide df1 by df2 where the row is broadcast but the column labels are respected.
A B C D
x 1 2 3 4
y 5 6 7 8
z 9 10 11 12
A B D C
q 0 1 2 3
This would be wrong.
df1.values/df2.values
[[ inf 2. 1.5 1.33333333]
[ inf 6. 3.5 2.66666667]
[ inf 10. 5.5 4. ]]
Answer I desire is:
A B C D
x inf 2 1 2
y inf 6 2.33 4
z inf 10 3.66 6
div() method divides element-wise division of one pandas DataFrame by another. DataFrame elements can be divided by a pandas series or by a Python sequence as well. Calling div() on a DataFrame instance is equivalent to invoking the division operator (/).
The simple division (/) operator is the first way to divide two columns. You will split the First Column with the other columns here. This is the simplest method of dividing two columns in Pandas. We will import Pandas and take at least two columns while declaring the variables.
To divide each column by a particular column, we can use division sign (/). For example, if we have a data frame called df that contains three columns say x, y, and z then we can divide all the columns by column z using the command df/df[,3].
std() function to calculate the standard deviation of values in a pandas DataFrame. Note that the std() function will automatically ignore any NaN values in the DataFrame when calculating the standard deviation.
If you divide by a Series (by selecting that one row of the second dataframe), pandas will align this series on the columns of the first dataframe, giving the desired result:
In [75]: df1 / df2.loc['q']
Out[75]:
A B C D
x inf 2 1.000000 2
y inf 6 2.333333 4
z inf 10 3.666667 6
If you don't know/want to use the name of that one row, you can use squeeze
to convert the one-column dataframe to a series: df1 / df2.squeeze()
(see answer of @EdChum).
May be, you could order your df2
columns same of df1
and then divide on values
In [53]: df1.values/df2[df1.columns].values
Out[53]:
array([[ inf, 2. , 1. , 2. ],
[ inf, 6. , 2.33333333, 4. ],
[ inf, 10. , 3.66666667, 6. ]])
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