How to add already created figures to a subplot figure

Question

I created this function that generates the ROC_AUC, then I returned the figure created to a variable.

from sklearn.metrics import roc_curve, auc
from sklearn.preprocessing import label_binarize
import matplotlib.pyplot as plt

def plot_multiclass_roc(clf, X_test, y_test, n_classes, figsize=(17, 6)):
    y_score = clf.decision_function(X_test)

    # structures
    fpr = dict()
    tpr = dict()
    roc_auc = dict()

    # calculate dummies once
    y_test_dummies = pd.get_dummies(y_test, drop_first=False).values
    for i in range(n_classes):
        fpr[i], tpr[i], _ = roc_curve(y_test_dummies[:, i], y_score[:, i])
        roc_auc[i] = auc(fpr[i], tpr[i])

    # roc for each class
    fig, ax = plt.subplots(figsize=figsize)
    ax.plot([0, 1], [0, 1], 'k--')
    ax.set_xlim([0.0, 1.0])
    ax.set_ylim([0.0, 1.05])
    ax.set_xlabel('False Positive Rate')
    ax.set_ylabel('True Positive Rate')
    ax.set_title('Receiver operating characteristic for Optimized SVC model')
    for i in range(n_classes):
        ax.plot(fpr[i], tpr[i], label='ROC curve (area = %0.2f) for label %i' % (roc_auc[i], i+1))
    ax.legend(loc="best")
    ax.grid(alpha=.4)
    sns.despine()
    plt.show()
    return fig

svc_model_optimized_roc_auc_curve = plot_multiclass_roc(svc_model_optimized, X_test, y_test, n_classes=3, figsize=(16, 10))

The resulting figure would look like somethin below:

I created 5 different ROC curves for 5 different models using the same function but returning their figures to separate variables.

Then I created a subplot figure that I thought would display all of them. The code is:

import matplotlib.pyplot as plt
%matplotlib inline

figs, ax = plt.subplots(
    nrows=3,
    ncols=2,
    figsize=(20, 20),
)

ax[0,0] = logmodel_roc_auc_curve
ax[0,1] = RandomForestModel_optimized_roc_auc_cruve
ax[1,0] = decisiontree_model_optimized_roc_auc_curve
ax[1,1] = best_clf_knn_roc_auc_curve
ax[2,0] = svc_model_optimized_roc_auc_curve

But the resulting figure produced is this:

There was a similar problem to this here
but it was solved by executing the functions again. But I would like to find a way if possible to just simply "paste" the figures I already have into the subplot.

Asked By: JOHN EDWARD BINAY

||

Source

Answer 1

You need exactly the same as in the linked solution. You can’t store plots for later use. Note that in matplotlib a figure is the surrounding plot with one or more subplots. Each subplot is referenced via an ax.

Function plot_multiclass_roc needs some changes:

it needs an ax as parameter, and the plot should be created onto that ax.
fig, ax = plt.subplots(figsize=figsize) should be removed; the fig should be created previously, outside the function
also plt.show() should be removed from the function
it is not necessary to return anything

Outside the function, you create the fig and the axes. In matplotlib there is a not-well-followed convention to use axs for the plural of ax (when referring to a subplot). So:

fig, axs = plt.subplots(nrows = 3,
                        ncols = 2,
                        figsize= (20, 20)
                       )
plot_multiclass_roc(...., ax=axs[0,0]) # use parameters for logmodel
plot_multiclass_roc(...., ax=axs[0,1]) # use parameters for Random Forest
plot_multiclass_roc(...., ax=axs[1,0]) # ...
plot_multiclass_roc(...., ax=axs[1,1]) # ...
plot_multiclass_roc(...., ax=axs[2,0]) # ...
axs[2,1].remove() # remove the unused last ax
plt.tight_layout()  # makes that labels etc. fit nicely
plt.show()

Answered By: JohanC

How to add already created figures to a subplot figure

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