interpret.py

#AUTOGENERATED! DO NOT EDIT! File to edit: dev/20_interpret.ipynb (unless otherwise specified).

__all__ = ['plot_top_losses', 'Interpretation', 'ClassificationInterpretation']

#Cell
from .test import *
from .data.all import *
from .optimizer import *
from .learner import *

#Cell
@typedispatch
def plot_top_losses(x, y, *args, **kwargs):
    raise Exception(f"plot_top_losses is not implemented for {type(x)},{type(y)}")

#Cell
class Interpretation():
    "Interpretation base class, can be inherited for task specific Interpretation classes"
    def __init__(self, dl, inputs, preds, targs, decoded, losses):
        store_attr(self, "dl,inputs,preds,targs,decoded,losses")

    @classmethod
    def from_learner(cls, learn, ds_idx=1, dl=None, act=None):
        "Construct interpretatio object from a learner"
        if dl is None: dl = learn.dbunch.dls[ds_idx]
        return cls(dl, *learn.get_preds(dl=dl, with_input=True, with_loss=True, with_decoded=True, act=None))

    def top_losses(self, k=None, largest=True):
        "`k` largest(/smallest) losses and indexes, defaulting to all losses (sorted by `largest`)."
        return self.losses.topk(ifnone(k, len(self.losses)), largest=largest)

    def plot_top_losses(self, k, largest=True, **kwargs):
        losses,idx = self.top_losses(k, largest)
        if not isinstance(self.inputs, tuple): self.inputs = (self.inputs,)
        if isinstance(self.inputs[0], Tensor): inps = tuple(o[idx] for o in self.inputs)
        else: inps = self.dl.create_batch(self.dl.before_batch([tuple(o[i] for o in self.inputs) for i in idx]))
        b = inps + tuple(o[idx] for o in (self.targs if is_listy(self.targs) else (self.targs,)))
        x,y,its = self.dl._pre_show_batch(b, max_n=k)
        b_out = inps + tuple(o[idx] for o in (self.decoded if is_listy(self.decoded) else (self.decoded,)))
        x1,y1,outs = self.dl._pre_show_batch(b_out, max_n=k)
        if its is not None:
            plot_top_losses(x, y, its, outs.itemgot(slice(len(inps), None)), self.preds[idx], losses,  **kwargs)
        #TODO: figure out if this is needed
        #its None means that a batch knos how to show itself as a whole, so we pass x, x1
        #else: show_results(x, x1, its, ctxs=ctxs, max_n=max_n, **kwargs)

#Cell
class ClassificationInterpretation(Interpretation):
    "Interpretation methods for classification models."

    def __init__(self, dl, inputs, preds, targs, decoded, losses):
        super().__init__(dl, inputs, preds, targs, decoded, losses)
        self.vocab = self.dl.vocab
        if is_listy(self.vocab): self.vocab = self.vocab[-1]

    def confusion_matrix(self):
        "Confusion matrix as an `np.ndarray`."
        x = torch.arange(0, len(self.vocab))
        cm = ((self.decoded==x[:,None]) & (self.targs==x[:,None,None])).sum(2)
        return to_np(cm)

    def plot_confusion_matrix(self, normalize=False, title='Confusion matrix', cmap="Blues", norm_dec=2,
                              plot_txt=True, **kwargs):
        "Plot the confusion matrix, with `title` and using `cmap`."
        # This function is mainly copied from the sklearn docs
        cm = self.confusion_matrix()
        if normalize: cm = cm.astype('float') / cm.sum(axis=1)[:, np.newaxis]
        fig = plt.figure(**kwargs)
        plt.imshow(cm, interpolation='nearest', cmap=cmap)
        plt.title(title)
        tick_marks = np.arange(len(self.vocab))
        plt.xticks(tick_marks, self.vocab, rotation=90)
        plt.yticks(tick_marks, self.vocab, rotation=0)

        if plot_txt:
            thresh = cm.max() / 2.
            for i, j in itertools.product(range(cm.shape[0]), range(cm.shape[1])):
                coeff = f'{cm[i, j]:.{norm_dec}f}' if normalize else f'{cm[i, j]}'
                plt.text(j, i, coeff, horizontalalignment="center", verticalalignment="center", color="white" if cm[i, j] > thresh else "black")

        ax = fig.gca()
        ax.set_ylim(len(self.vocab)-.5,-.5)

        plt.tight_layout()
        plt.ylabel('Actual')
        plt.xlabel('Predicted')
        plt.grid(False)

    def most_confused(self, min_val=1):
        "Sorted descending list of largest non-diagonal entries of confusion matrix, presented as actual, predicted, number of occurrences."
        cm = self.confusion_matrix()
        np.fill_diagonal(cm, 0)
        res = [(self.vocab[i],self.vocab[j],cm[i,j])
                for i,j in zip(*np.where(cm>=min_val))]
        return sorted(res, key=itemgetter(2), reverse=True)