Creating A Boxplot Facetgrid In Seaborn For Python

I'm trying to create a 4x4 FacetGrid in seaborn for 4 boxplots, each of which is split into 3 boxplots based on the iris species in the iris dataset. Currently, my code looks like

Solution 1:

Not a direct answer to your error, but if you are going to use seaborn, you should try to stick with "long" or "tidy" data (https://seaborn.pydata.org/tutorial/data_structure.html#long-form-data).

I'm assuming your original data set is wide (column for each feature of the observation). If you melt the data set like so:

iris = iris.melt(id_vars='target')

print(iris.head())

   target           variable  value
0  setosa  sepal length (cm)    5.11  setosa  sepal length (cm)    4.92  setosa  sepal length (cm)    4.73  setosa  sepal length (cm)    4.64  setosa  sepal length (cm)    5.0

You'll be able to use seaborn's catplot with kind='box'

sns.catplot(
    data=iris, x='target', y='value',
    col='variable', kind='box', col_wrap=2
)

Solution 2:

axes shape is (nrows, ncols). In this case is:

array([[<matplotlib.axes._subplots.AxesSubplot object at 0x7f4267f425f8>,
        <matplotlib.axes._subplots.AxesSubplot object at 0x7f4267f1bb38>],
       [<matplotlib.axes._subplots.AxesSubplot object at 0x7f4267ec95c0>,
        <matplotlib.axes._subplots.AxesSubplot object at 0x7f4267ef9080>]],
      dtype=object)

So, when you do ax=axes[0] you get a array and not the axes. Try:

fig, axes = plt.subplots(2, 2)

ax = sns.boxplot(x="Species", y="SepalLengthCm", data=iris, orient='v', 
    ax=axes[0, 0])
ax = sns.boxplot(x="Species", y="SepalWidthCm", data=iris, orient='v', 
    ax=axes[0, 1])
ax = sns.boxplot(x="Species", y="PetalLengthCm", data=iris, orient='v', 
    ax=axes[1, 0])
ax = sns.boxplot(x="Species", y="PetalWidthCm", data=iris, orient='v', 
    ax=axes[1, 1])

Solution 3:

Because as @Lucas points out that axes returns a numpy array of 2D(nrows, ncols), you can flatten this array 1D using:

axes=axes.flatten()

And, you can keep your same code like this:

fig, axes = plt.subplots(2, 2)
axes = axes.flatten()

ax = sns.boxplot(x="Species", y="SepalLengthCm", data=iris, orient='v', 
    ax=axes[0])
ax = sns.boxplot(x="Species", y="SepalWidthCm", data=iris, orient='v', 
    ax=axes[1])
ax = sns.boxplot(x="Species", y="PetalLengthCm", data=iris, orient='v', 
    ax=axes[2])
ax = sns.boxplot(x="Species", y="PetalWidthCm", data=iris, orient='v', 
    ax=axes[3])

Output:

Solution 4:

Or just making the above more concise:

cat_variables = ['SepalLengthCm', 'SepalWidthCm', 'PetalLengthCm', 'PetalWidthCm']
x_var = "Species"
fig, axes = plt.subplots(len(cat_variables)/2, len(cat_variables)/2, figsize=(15,15))
axes = axes.flatten()

i = 0for t in cat_variables:
    ax = sns.boxplot(x=x_var, y=TARGET, data=iris, orient='v', 
    ax=axes[i])
    i +=1