Turi Create - Please use dropna() to drop rows - python-2.7

Question

I am having issues with Apple Turi Create and image classifier. I have successfully created a model with 22 categories. I have recently added 5 more categories and console is giving me error warning
Please use dropna() to drop rows with missing target values.
The full console log looks like this:
[16:30:30] src/nnvm/legacy_json_util.cc:190: Loading symbol saved by previous version v0.8.0. Attempting to upgrade...
[16:30:30] src/nnvm/legacy_json_util.cc:198: Symbol successfully upgraded!
Resizing images...
Performing feature extraction on resized images...
Premature end of JPEG file
Completed 512/1883
Completed 1024/1883
Completed 1536/1883
Completed 1883/1883
PROGRESS: Creating a validation set from 5 percent of training data. This may take a while.
You can set ``validation_set=None`` to disable validation tracking.
[ERROR] turicreate.toolkits._main: Toolkit error: Target column has missing value.
Please use dropna() to drop rows with missing target values.
Traceback (most recent call last):
File "train.py", line 8, in <module>
model = tc.image_classifier.create(train_data, target='label', max_iterations=1000)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/turicreate/toolkits/image_classifier/image_classifier.py", line 132, in create
verbose=verbose)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/turicreate/toolkits/classifier/logistic_classifier.py", line 312, in create
seed=seed)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/turicreate/toolkits/_supervised_learning.py", line 397, in create
options, verbose)
File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/turicreate/toolkits/_main.py", line 75, in run
raise ToolkitError(str(message))
turicreate.toolkits._main.ToolkitError: Target column has missing value.
Please use dropna() to drop rows with missing target values.
I have upgraded turi and coremltools to the lates versions, but I don't know where I should implement the dropna() in the code. I only found this reference and followed the code.
It looks like this:
data.py
import turicreate as tc
image_data = tc.image_analysis.load_images('images', with_path=True)
labels = ['A', 'B', 'C', 'D']
def get_label(path, labels=labels):
for label in labels:
if label in path:
return label
image_data['label'] = image_data['path'].apply(get_label)
#import os
#image_data['label'] = image_data['path'].apply(lambda path: os.path.dirname(path).split('/')[-1])
image_data.save('boxes.sframe')
image_data.explore()
train.py
import turicreate as tc
data = tc.SFrame('boxes.sframe')
data.dropna()
train_data, test_data = data.random_split(0.8)
model = tc.image_classifier.create(train_data, target='label', max_iterations=1000)
predictions = model.classify(test_data)
results = model.evaluate(test_data)
print "Accuracy : %s" % results['accuracy']
print "Confusion Matrix : \n%s" % results['confusion_matrix']
model.save('boxes.model')
How do I drop all the empty columns and rows please? Does the max_iterations=1000 have also effect on the error?
Thank you for suggestions

Answer 1

data.dropna() isn't done in place, you need to write it: data = data.dropna()
See documentation here https://apple.github.io/turicreate/docs/api/generated/turicreate.SFrame.dropna.html