Creating a boxplot FacetGrid in Seaborn for python

问题

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 this:

sns.set(style="whitegrid")
iris_vis = sns.load_dataset("iris")

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

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])

However, I'm getting this error from my interpreter:

AttributeError: 'numpy.ndarray' object has no attribute 'boxplot'

I'm confused on where the attribute error is exactly in here. What do I need to change?

回答1:

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])

回答2:

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:

回答3:

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

来源：https://stackoverflow.com/questions/52472757/creating-a-boxplot-facetgrid-in-seaborn-for-python

标签

python

data-visualization

seaborn

data-science

boxplot