## Python: Scaling numbers column by column with pandas

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I have a Pandas data frame 'df' in which I'd like to perform some scalings column by column.

- In column 'a', I need the maximum number to be 1, the minimum number to be 0, and all other to be spread accordingly.
- In column 'b', however, I need the
**minimum number to be 1**, the**maximum number to be 0**, and all other to be spread accordingly.

Is there a Pandas function to perform these two operations? If not, numpy would certainly do.

a b A 14 103 B 90 107 C 90 110 D 96 114 E 91 114

You could subtract by the min, then divide by the max (beware 0/0). Note that after subtracting the min, the new max is the original max - min.

In [11]: df Out[11]: a b A 14 103 B 90 107 C 90 110 D 96 114 E 91 114 In [12]: df -= df.min() # equivalent to df = df - df.min() In [13]: df /= df.max() # equivalent to df = df / df.max() In [14]: df Out[14]: a b A 0.000000 0.000000 B 0.926829 0.363636 C 0.926829 0.636364 D 1.000000 1.000000 E 0.939024 1.000000

To switch the order of a column (from 1 to 0 rather than 0 to 1):

In [15]: df['b'] = 1 - df['b']

*An alternative method is to negate the b columns first ( df['b'] = -df['b']).*

**Python: Scaling numbers column by column with pandas,** You could subtract by the min, then divide by the max (beware 0/0). Note that after subtracting the min, the new max is the original max - min. Scaling and normalizing a column in Pandas python Scaling and normalizing a column in pandas python is required, to standardize the data, before we model a data. We will be using preprocessing method from scikitlearn package. Lets see an example which normalizes the column in pandas by scaling

This is how you can do it using `sklearn`

and the `preprocessing`

module. Sci-Kit Learn has many pre-processing functions for scaling and centering data.

In [0]: from sklearn.preprocessing import MinMaxScaler In [1]: df = pd.DataFrame({'A':[14,90,90,96,91], 'B':[103,107,110,114,114]}).astype(float) In [2]: df Out[2]: A B 0 14 103 1 90 107 2 90 110 3 96 114 4 91 114 In [3]: scaler = MinMaxScaler() In [4]: df_scaled = pd.DataFrame(scaler.fit_transform(df), columns=df.columns) In [5]: df_scaled Out[5]: A B 0 0.000000 0.000000 1 0.926829 0.363636 2 0.926829 0.636364 3 1.000000 1.000000 4 0.939024 1.000000

**pandas dataframe columns scaling with sklearn,** This following snippet works perfectly and produces exact output without having to use apply. import pandas as pd. from sklearn.preprocessing I have a Pandas data frame 'df' in which I'd like to perform some scalings column by column. In column 'a', I need the maximum number to be 1, the minimum number to be 0, and all other to be spread accordingly. In column 'b', however, I need the minimum number to be 1, the maximum number to be 0, and all other to be spread accordingly.

This is not very elegant but the following works for this two column case:

#Create dataframe df = pd.DataFrame({'A':[14,90,90,96,91], 'B':[103,107,110,114,114]}) #Apply operates on each row or column with the lambda function #axis = 0 -> act on columns, axis = 1 act on rows #x is a variable for the whole row or column #This line will scale minimum = 0 and maximum = 1 for each column df2 = df.apply(lambda x:(x.astype(float) - min(x))/(max(x)-min(x)), axis = 0) #Want to now invert the order on column 'B' #Use apply function again, reverse numbers in column, select column 'B' only and #reassign to column 'B' of original dataframe df2['B'] = df2.apply(lambda x: 1-x, axis = 1)['B']

If I find a more elegant way (for example, using the column index: (0 or 1)mod 2 - 1 to select the sign in the apply operation so it can be done with just one apply command, I'll let you know.

**Scaling and normalizing a column in Pandas python,** Scaling and normalizing a column in pandas python : Example scale a column in pandas python. normalize a column Lets see an example which normalizes the column in pandas by scaling float_array = df[ 'Score' ].values.astype( float ) I have a pandas dataframe with mixed type columns, and I'd like to apply sklearn's min_max_scaler to some of the columns. Ideally, I'd like to do these transformations in place, but haven't figured out a way to do that yet. I've written the following code that works: import pandas as pd. import numpy as np. from sklearn import preprocessing

In case you want to scale only one column in the dataframe, you can do the following:

from sklearn.preprocessing import MinMaxScaler scaler = MinMaxScaler() df['Col1_scaled'] = scaler.fit_transform(df['Col1'].values.reshape(-1,1))

**Normalize A Column In pandas,** Try my machine learning flashcards or Machine Learning with Python Cookbook. Import required modules import pandas as pd from sklearn import Create an example dataframe with a column of unnormalized data data x the 'scores' column's values as floats x = df[['score']].values.astype(float) # Import required modules import pandas as pd from sklearn import preprocessing # Set charts to view inline % matplotlib inline Create Unnormalized Data # Create an example dataframe with a column of unnormalized data data = { 'score' : [ 234 , 24 , 14 , 27 , - 74 , 46 , 73 , - 18 , 59 , 160 ]} df = pd .

given a data frame

df = pd.DataFrame({'A':[14,90,90,96,91], 'B':[103,107,110,114,114]})

scale with mean 0 and var 1

df.apply(lambda x: (x - np.mean(x)) / np.std(x), axis=0)

scale with range between 0 and 1

df.apply(lambda x: x / np.max(x), axis=0)

**How to scale Pandas DataFrame columns with the scikit-learn ,** Min-max scaling is a common feature pre-processing technique which results in scaled data values that fall in the range [0,1] . When applied to a Python sequence Data play a major role in data analytics and data science . It is definitely the basis of all the process in these eco space . This blog is going to talk about feature scaling . what is it ? , why

**Scaling to large datasets,** The default pandas data types are not the most memory efficient. This is especially true for text data columns with relatively few unique values (commonly referred Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Learn more select columns based on columns names containing a specific string in pandas

**Rescaling Data,** 61.3, 61.7, 74.4, 76.5, 60.7] In [3]: import pandas as pd In [4]: data_df = pd. We can put them on the same scale by making their minimum be zero and their maximum be one. Subtract from every item in a column the minimum of that column changing our source data, let's make new columns for these rescaled values. Your Pandas Dataframe is now normalized only at the columns you want However , if you want the opposite , select a list of columns that you DON'T want to normalize, you can simply create a list of all columns and remove that non desired ones

**datas-frame – Modern Pandas (Part 8): Scaling,** Historically, pandas users have scaled to larger datasets by switching away from pandas or using iteration. Both of these are Dask is an open-source project that natively parallizes Python. I'm a happy Select the occupation column ( __getitem__ ); Perform the value counts; Select the 100 largest values. Python Pandas - Understanding inplace=True. 0 votes . Python: Scaling numbers column by column with pandas. asked Oct 5, 2019 in Data Science by sourav (17.6k points)

##### Comments

- You'd need to take
`1-`

for`b`

, though. - You'll need to mess with the
`b`

column to get things flipped. I'd say multiply by -1, apply the sub and div, then multiply by -1 again. - @TomAugspurger actually I think flipping is more elegant, you only need to do it before! :)
- If not writing a Pipeline, it's simpler to use
`minmax_scale(df)`

rather than`MinMaxScaler`

. - The answered formula for scaling between 0 and 1 doesn't take the min into account. Also, what if max is 0?