The blood transfusion dataset¶
In this notebook, we will present the “blood transfusion” dataset. This
dataset is locally available in the directory
datasets and it is stored as
a comma separated value (CSV) file. We start by loading the entire dataset.
import pandas as pd blood_transfusion = pd.read_csv("../datasets/blood_transfusion.csv")
We can have a first look at the at the dataset loaded.
In this dataframe, we can see that the last column correspond to the target
to be predicted called
"Class". We will create two variables,
target to separate the data from which we could learn a predictive model
target that should be predicted.
data = blood_transfusion.drop(columns="Class") target = blood_transfusion["Class"]
Let’s have a first look at the
We observe four columns. Each record corresponds to a person that intended to give blood. The information stored in each column are:
Recency: the time in months since the last time a person intended to give blood;
Frequency: the number of time a person intended to give blood in the past;
Monetary: the amount of blood given in the past (in c.c.);
Time: the time in months since the first time a person intended to give blood.
Now, let’s have a look regarding the type of data that we are dealing in these columns and if any missing values are present in our dataset.
<class 'pandas.core.frame.DataFrame'> RangeIndex: 748 entries, 0 to 747 Data columns (total 4 columns): # Column Non-Null Count Dtype --- ------ -------------- ----- 0 Recency 748 non-null int64 1 Frequency 748 non-null int64 2 Monetary 748 non-null int64 3 Time 748 non-null int64 dtypes: int64(4) memory usage: 23.5 KB
Our dataset is made of 748 samples. All features are represented with integer numbers and there is no missing values. We can have a look at each feature distributions.
_ = data.hist(figsize=(12, 10), bins=30, edgecolor="black", density=True)
/opt/hostedtoolcache/Python/3.7.10/x64/lib/python3.7/site-packages/pandas/plotting/_matplotlib/tools.py:400: MatplotlibDeprecationWarning: The is_first_col function was deprecated in Matplotlib 3.4 and will be removed two minor releases later. Use ax.get_subplotspec().is_first_col() instead. if ax.is_first_col():
There is nothing shocking regarding the distributions. We only observe a high
value range for the features
means that we have a few extreme high values for these features.
Now, let’s have a look at the target that we would like to predict for this task.
0 donated 1 donated 2 donated 3 donated 4 not donated Name: Class, dtype: object
import matplotlib.pyplot as plt target.value_counts(normalize=True).plot.barh() plt.xlabel("Number of samples") _ = plt.title("Class distribution")
We see that the target is discrete and contains two categories: whether a
"not donated" his/her blood. Thus the task to be
solved is a classification problem. We should note that the class counts of
these two classes is different.
not donated 0.762032 donated 0.237968 Name: Class, dtype: float64
Indeed, ~76% of the samples belong to the class
"not donated". It is rather
important: a classifier that would predict always this
"not donated" class
would achieve an accuracy of 76% of good classification without using any
information from the data itself. This issue is known as class imbalance. One
should take care about the statistical performance metric used to evaluate a
model as well as the predictive model chosen itself.
Now, let’s have a naive analysis to see if there is a link between features and the target using a pair plot representation.
import seaborn as sns _ = sns.pairplot(blood_transfusion, hue="Class")
Looking at the diagonal plots, we don’t see any feature that individually
could help at separating the two classes. When looking at a pair of feature,
we don’t see any stricking combinations as well. However, we can note that
"Frequency" features are perfectly correlated: all the
data points are aligned on a diagonal.
As a conclusion, this dataset would be a challenging dataset: it suffer from class imbalance, correlated features and thus very few features will be available to learn a model, and none of the feature combinations were found to help at predicting.